In my story, the world has come to a point where technology has advanced a bit farther than what we have now but the ecosystem is in a terrible state. With the aid of magic, one of the characters manages to reverse the effect humanity has had on the planet, basically removing anything that harmed the world or that people have done. Geography is altered, houses vanish, communication is shut down. All there is is the people and animals. Magic is gone too, it was all used to destroy technology. The result is that the people are no longer united and technology is nonexistent, but aside from that, what major things would happen? What would the world look like?
In the short term, you will have chaos, starvation, and fighting over food. B/c so few people know how to get food in the wild. And b/c without modern technology, the planet can sustain a lot fewer people than it has.
Eventually, civilization will rebuild itself. For every piece of technology, there are be people who know how to make it. For every raw material, there are people who know how to obtain them from nature. Your reset will restore all the easily accessible mineral deposits.
It is true that in the first few weeks, brute force will rule. But soon enough, a newly formed tribe of big & strong men will be defeated by a tribe of men who know how to make bows. And they in turn be defeated by whoever learns to make metals.
Nations will re-form, mainly along language boundaries. Economy will be rebuilt, b/c so many people want to be able to buy whatever they need.
Just like a bad dream, the characters remember that reality and history. The traumas are different from one person to other. Some people see it as a new opportunity but for other is like death, to be in a place we're they don't want to be, yes, everything around "is better" but is not what they want. People be people, so the criminals or "bad" people are the ones that are trying to take advantage(once again?)... The world looks like a desert(Mars) or mostly water(Neptune).