If I was the supreme ruler of the world, what would you do to change the relationship between Mexico and the United States?

If I was supreme ruler of the world I would make it easier for immigrants to get visas and greencards. I just want to make it easier for immigrants to get to the United States so they don't have to die trying to cross the border illegaly. I would still have borders instead of taking all of them down because it could cause chaos and make the world worse.