At what point does an open border sorta make the government illegitimate? The state is just ignoring its own laws on this issue for one reason or another.
The issue is more that it is impossible to have an open border combined with any sort of welfare state. And there is a question about political compatibility - at some point there is a difference between individual migration and an invasion. But realistically, the US had the debate on this decades ago and has decided that insofar as there is a national culture it doesn't consider it threatened by migrants with foreign views. It is a bit late to get worried about it now for obvious reasons.
The governemnt gets to play both sides by making labour cheap and also campaigning "Build the Wall".
If any working/middle class people complain, the people who control the culture and media will ensure they get smeared as racists.
2. By living in states like California that did that Machiavellian 1-2 combo of allowing illegal immigrants to get drivers licenses, then made it so that people with a driver's license are automatically registered to vote.
Go ahead and produce evidence that votes were cast by ineligible people in California.
Even better if it's a significant enough number to indicate a systemic problem with the registration system.
Either the US goes genocidal and purge 3% of their population or they all get along. Getting along seems like the good option to me!
In the 80s when the Iron Curtain was up, we drove freely between some European countries, but certainly not East Germany.
Which of those governments was more "legitimate"?