The problem is that if the U.S. goes down so does the rest of the world. Some of this is the regional wars that we are likely to see once the U.S. withdraws from its position as peacemaker (like Russia/Ukraine), some of it is economic damage from the collapse of globalization (a la Straight of Hormuz), some of it is direct threats (like Trump threatening to annex Canada and invade Greenland). If we're really stupid some of it might even be nuclear annihilation - superpowers don't go down easily, and MAD requires that the nuclear armed powers have a future that they seek to preserve. Russia is a significant risk here too - demographically they're done in a generation, and countries that are going to fail anyway don't have much of an incentive to keep the current world intact.

Given that the current world order is likely toast, I'd rather hole up in my current spot, where I've got family, friends, a home, and knowledge of the local environment and culture. Plus it's got a relatively forgiving climate, fertile soil, natural harbors, two oceans for defense, an educated populace whose values aren't too different from mine, and a set of mountain ranges if we need to defend ourselves from the rest of the former U.S. Geographically it's hard to do better than the territory occupied by what is currently the United States.