As alluded to by Ian, some would approach with caution, while others, as alluded to by Gary, would be far more bullish.
There are untold reasons why one should be cautious, not the least of which is the potential for world destroying paradoxes.
Unknown effects on our physical world
We would have no way of knowing what potential disaster could unfold from use of this technology. Could it tear at the very fabric of space and time, ripping apart our world? Was it merely luck that the chrononaut who has to come to visit us from the future even made it here in the first place without causing irreparable damage?
Whether or not these thoughts would occur to Presidents, MPs or Senators, they would come to the minds of scientists and activists that sit on advisory panels or leader multinational NGOs, and international research institutes. As such there would be a healthy body of people pressuring leaders into methodically researching any potential adverse effects of the technology on the user, and the world as a whole.
It's not just present day world governments who might seek power, and meddling in the affairs of the chrononaut and his technology might cause an outrage in the future leading to potential repercussive actions. I am thinking of a few Star Trek plots which revolve around guardians of space-time who prevent any interference in timelines. Who can say whether or not any attempted interfering with the time traveler and his technology isn't being monitored in the future. Governments would be right to be concerned with this possibility.
I wont even go into detail as I think he are aware of this. But For reasons similar to ' Unknown effects on our physical world' I can see a fair amount of public pressure to investigate these.
presumable some dialogue would occur between our time traveler and world governments on their own findings from the future on these issues, but I am sure we would try and verify them for the sake of understanding and reassurance.
For a variety of reasons some nations would probably have little reaction to the news.
There reasons are varied, whether it would count as blasphemy, or it comes across as an impossibility, majorities in some nations would assuredly refuse to believe it as a true event.
Some governments would accept this as a true, and move on with the matter of the day do to overwhelming pressure to deal with current and very troubling affairs. It may become a back burner issue for nations dealing with disease and famine (even if it presents an opportunity to resolve these issues another way)
More to Gary's point, whether open about it, or keeping it a secret, undoubtedly some nations will seek to control what is the greatest potential military and economic leap forward ever presented to mankind.
Some may openly call for its control to have a tool to help prevent complete exploitation by those in the future who now many control our past and as such our futures. This could easily lead to both unilateral and multilateral actions to attempt and control this technology.
Some would seek the technology to gain the upper hand against present day enemies. They may even use the guise of controlling the technology to counter those from future, while truly maintaining eyes on today.
Whether or not that is through force or negotiation is inevitably up to the whims of your nations, and the perceived nature of the time traveler.
Those who have the power may try through military means to gain access to the technology and time traveler.
More interesting would be those who seek to control it covertly. I could see nations trying to bribe or seduce the time traveler to gain access. Or perhaps nations look forward, planning multi-generational infiltration plans to gaining access to the not-yet-invented machine. To that point perhaps out time traveler is a spy from one of these programs (The paradoxes begin)