For many of those that don't, that's a choice. Keep in mind that emigrating doesn't necessarily mean adhering to all the bureaucratic procedures involved, all the time.
I lived in my home country and then Botswana for nearly 30 years. I've been in the US for over 30 years. I don't anticipate many more moves.
It’s more than the combined population of the top ten megacities (pop. > 20 million) in the world.
In addition to that, immigrants and refugees are having an outsized influence on politics, and on who gets elected, in many countries around the world.
It’s denying reality to say it “hardly matters”.
Why do you think so? Most developed and democratic countries are in trouble, lately. Instability is everywhere. T
Also, the US situation was exacerbated by a number of factors unique to the US: "corporations are people", "money is speech", the two-party, first past the post voting system, the electoral college, and the specifics of the representation system, are all huge disadvantages for achieving good democratic outcomes.
Plus, I think there's a good chance that the more progressive European countries will learn from, and be inoculated by, the US mistakes. I didn't leave Europe for political reasons, I left for business reasons, so I don't have any serious concerns about returning.
Finally, I don't have very many decades left.
You have my applause. But that certainly looks like you are in for a lot of moving around, going forward. I guess it is not an option for everyone.