I do NOT know anything about video games, but I think that if you want to restart a game, you push the "reset" button. Am I right?
So let's say that the United States and Russia are playing a video game. Let's say that one of the countries is losing the game. Maybe the other country will be very nice and say, "OK. Let's push the reset button and start the game again."
In other words, for many years relations between your country and my country have not always been smooth. So a few years ago, many Americans said something like: Let's push the reset button. (That is, let's forget what has happened in the past between our two countries. Let's start from 0.)