The answer here is simple. Colonies. As a modern man in 1300 C.E. France, Bob, and Bob alone in mainland Europe, has access to the single most valuable piece of knowledge in geopolitical history—the existence of the American continents.
So what does Bob do? He invests in explorers and navigators, similar to what the rulers of Portugal did in the fifteenth century in Africa, except he instructs them to head westward, not southward. Some, to be sure, think this is suicide—after all, fourteenth century sailors don’t even know of the trade winds that would take them home, but there will always be someone in the country adventurous enough to take the risk. It won’t be easy for Bob to get off the ground, though, sailing technology was not as good in 1300 as it was in 1492. Bob’s noble rivals, like most educated Europeans at the time, understand the world is round, so they don’t think Bob is batshit crazy, but at the same time, they dismiss it as just another pet hobby of the king and privately gossip amongst themselves about how stupid the king is to send ships into empty water. They don’t anticipate any threat to their power.
1. Gold, Bob, and Glory
Then, one of Bob’s explorers comes back with news of a strange new land far across the ocean. Most likely, if they set out from France, his captain landed somewhere in Canada or New England and Bob is told that the land is cold, barren, uninteresting, and devoid of any precious metals worth mining. But Bob doesn’t give up. He sends more navigation parties out radially from France, knowing that the continent extends continuously for the entire length of Europe and Africa. Subsequent expeditions find the Caribbean, Mexico, Bolivia, Brazil, and all the accompanying treasures within. Colorful birds, Native American souvenirs, news of an entirely new land, all of this excites the populace. The serfs who previously knew of no greater life outside of their manor, are now clamoring for a taste of the great new world. Bob, who is now looking for loyal colonists, has no shortage of volunteers. Because they are mostly poor peasants with nothing to lose, most of his volunteers are loyal to Bob, and Bob alone.
2. Sorry, Pocahontas.
First, Bob needs to deal with the Native Americans. Despite any progressive quips he might have inherited from the 21st century, this choice is already made for him. Disease wipes out the Native Americans whether or not he wants to. The rest are reduced to bands of survivors, wandering what is, to them, a post apocalyptic world with an alien invasion thrown in—something of a mix between the Walking Dead and Falling Skies. Bob is now free to move in with his forces.
Millions of natives are still around, and more than a few attempt to mount a resistance, but Bob has knowledge of something called “gunpowder”, and he instructs his tinkerers and alchemists to start improving upon the strange explosive dust coming over from the Middle East at the time. His tinkerers, psychologically, are also benefiting from the expanded horizons resulting from the discovery of a new continent, and so they start experimenting and hacking. Soon, Bob has new explosives, new alloys, new weapons, etc. The Native Americans, never much of a match to begin with, are steamrolled by Bob’s armies, who, with their new military technologies, Bob also uses against the nobles in France. If he is smart, he swiftly takes them out before they have a chance to adopt and incorporate his new weapons into their own armies. If he is really smart, Bob the Atheist uses the existence of the New World to discredit the church & expels the Catholic clergy from the country as a “cult of liars and conspirators”.
3. Bob the Athiest
The Pope, never as powerful to begin with as we usually imagine him to be in this time period, is helpless to stop it, as Bob’s neighbors in Germany, Spain, and England start hatching their own plots to expel the church. Kings and nobles across Europe are very interested in this new “I don’t have to listen to the Pope anymore!” idea. The Protestant Reformation comes early.
Now, Bob’s power is vastly magnified. He has land. He has natural resources. He has weapons. He has exclusive divine right, from expelling the Catholic church. He has money, from the silver mines of Mexico and Bolivia. (The silver messes with his economy for a little while, but that’s fine because all of Bob’s rivals in Europe are affected too.) Because he has land, he has the loyalty of the population, since he can gift peasants with their own land in the New World in exchange for service. Because he has the loyalty of the people, he has an army.
4. Liberté, Égalité, Roberté: How Bob protects his empire
Now, Bob puts his knowledge of 21st century civil rights and liberties to use. He teaches his people about natural rights, about freedom, about democracy. He promises that his colonies will become republican utopias for the poor. The people also begin to take an interest in education, since they now have a vision of becoming men and women into themselves. They begin valuing rights and freedoms, and the new education fad doesn’t hurt Bob’s ability to get new military or health technologies either. Bob’s people quickly become the most educated, healthy, and wealthy people in Europe (though at the time, this isn’t exactly a high bar to clear). But even more important than that, his people are transformed from subjects to citizens. And that gives Bob, and Bob alone, access to the most terrifying force in world history—the citizen army.
The citizen soldier isn’t like the your typical mercenary in a king or noble’s army. The citizen soldier is motivated. He (not she; Bob’s technology and social cohesion is still not sufficient to launch a full blown women’s rights revolution) is willing to die for his country. And not just his country. Just as Bob invents the citizen in this timeline, Bob also invents the nation state. The nation state is not like anything else in Europe, or many thousands of miles from Europe. (China was a nation state many times in its history, but China is China, and very far from Europe.) His people pledge allegiance to the flag of France, everything it represents, and by extension to Bob. To his citizens, France is no longer just the place they live, it’s an ideal, a cause worth dying for. It’s also transferable.
5. World Domination?
By now, the peasants in surrounding Europe have probably heard of the enlightenment Bob has set off, and a few demagogues amongst them may already be fomenting revolutions. If Bob is smart, he preempts them. Bob knows if the King of Castille (Spain isn’t one country yet even) gets overthrown by the local demagogues, his own French constitutional monarchy is probably next, since these revolutions have a habit of spiraling out of control. Instead, Bob uses this to his advantage. He invites the people of Spain and Germany to “join France”. Remember, he now runs a nation state, not a country, and just because you speak Spanish or German doesn’t mean you aren’t allowed to be a part of his new state. Bob casts himself as a liberator. The locals cheer on Bob’s armies as they take out their old rulers.
Most of the locals don’t mind being ruled by France, because they no longer see themselves as Castilian or Aragonese or English. Remember, Bob’s rival monarchs never managed to convert their own countries into nation states. The King of Spain (Castille) never had a chance to imprint his own flag on his people. France is the first state they know. And instead of seeing themselves as Castilian or French or English, his people see themselves as “Free Europeans”, with “Slave Europeans” as the out-group.
There will be no Treaty of Tordesillas. Bob is now head of a state that rules the entirety of Western Europe, and the Eastern and coastal portions of the Americas (it will take generations to settle the interior, but Bob has time). Bob is now at a crossroads. The enlightenment he has set off has not been lost on his colonists in the Americas. Bob himself probably has nothing to worry about. His colonists will be content to gorge on the plentiful land for perhaps a century if he is lucky. But, if no changes are made, they will eventually demand self-rule. If there is to be a central government, every citizen of Bob’s vast hemispherical nation must feel like they have a say in the composition of that government, and elections are very hard to hold when it still takes months to cross the Atlantic.
6. Who’s in charge?
Bob, a hero to his people, can probably get away with autocratic federal rule as “benevolent dictator for life” (with citizen legislatures in each province to provide democratic local rule), but his successor would certainly have to be democratically elected. The people would not automatically pledge allegiance to his son, although his son would probably have the best chance out of any candidate in a theoretical election. Quasi-hereditary rule is a bad precedent to set for the new democracy, but Bob would have to be of substantial character and republican virtue to instruct his people to not automatically “vote the bloodline”. Bob’s nation, having been built in a few decades, does not have the benefit of a long tradition of enlightenment and republican literature that the United States did in the 18th century, although the U.S. in the early 19th century does demonstrate it is possible for the populace to teach themselves a great deal of democratic ideology in a very short amount of time (~30–40 years).
7. “War against the brown people” vs. “The Federal Republic”
Bob’s successor would have two choices to preserve the unity of the nation. He could start a racial war against the “others”, further expanding the borders of “liberated” (and white) France across the world. Racism is a pretty recent invention, a product of the need to justify African slavery; for most of human history skin color was like any other physical trait—hair color, eye color, etc. What mattered was what was “inside”—religion, language, customs, etc. But even without the concept of racism, there would still be plenty of ways to stir up hatred against nonwhites in this timeline. Citizen armies would be fighting “savage” natives in the American interior, and “ignorant” Slavs and Arabs in Eurasia. A patriotic expansionary war would probably keep the secession genie in the bottle for a while, especially if it was portrayed as a war of liberation to spread democracy. But this would have to last until the communication technology caught up to make planetary democracy workable. Or the war could devolve into a war of perpetuity as the citizen armies come up against their limits in Africa and India.
Alternatively, Bob’s successor could devise a federal system capable of withstanding long communication times. This would be the more difficult, but also more sustainable solution. Each province of Greater France would elect four sets of representatives—two to form a local legislature, and two to represent the province in the central government in metropolitan France. Bob’s knowledge of bicameral legislatures proves very valuable in getting every citizen of Greater France to agree to this. Greater France becomes the Federal Republic of Greater France. The central government would initially be very weak, both by design and by circumstance, as the sheer distances involved make it unresponsive and remote. Most of the power would be vested in the regional legislatures. However, as communication and travel technology improves, the central government would become more and more powerful. You essentially have a single nation of white people ruling half the planet—unimaginable in our own timeline (though perfectly imaginable for anyone who has ever watched a sci-fi show with single-culture aliens).
8. What about everyone else?
It is interesting to think about what would happen to the rest of the world in the federal scenario. It is possible that an expansionary war would still be waged, although the leaders of the Federal Republic would probably be prudent to invest their resources in improving communication infrastructure rather than expanding the borders of an already overextended nation. More likely, the enlightenment ideals unleashed by Bob would travel beyond the French umbrella, but not across the entire globe. Arabs, Indians, and Chinese would all probably pose rough, though not impassable terrain for Bob’s democracy. You would probably see many small “vassal democracies” spring up along the borders of the Federal Republic in Russia and North Africa (Bob will be unable to colonize Sub-Saharan Africa for the same reasons that prevented European colonization in our timeline until the late 19th century).
The vassal democracies will be dwarfed by the vast Federal Republic and will be under its heavy influence, for economic reasons, if none other. They will mostly function as cultural and migratory buffers for the Federal Republic, and military buffers protecting the rest of the world. While small, the vassal democracies are nation states like the Federal Republic, and their populations will resist any attempt by the French to bring them under their direct military control. So they would hem in the enormous superstate on its northeastern border. Because smaller democracies would pop up as soon as Bob’s superstate stopped expanding, the Federal Republic would be unable to start expanding again if it ever stopped, something its leaders would be unlikely to foresee. Thus, it’s very possible that “One World Government” does not occur in this timeline.