They've done it in Europe. Nope it's a reality of our political system and its laws.
People can come and go as they please, work and live where they like.
Legal entry into one country is legal entry to all. That's not so difficult. But my parents, easy job and a goodly number of friends are here, and while I'm old, I'm not quite elderly. I wouldn't want to retire in America. I know what my passport gets me into.