Have you got a link for the border controls. Recently (May) a friend I know flew back from S.America to Paris, then overnight stay, train to Germany and UK. Five countries' borders, no checks anywhere.
No American has "one link" about border control. Let's just say that borders with our neighbors are at the least permeable of all my lifetime and that of all of my ancestors. I guess it's a relative thing. For years, you could just go in and out of Canada on many small roads, no problem. Then we jointly built cement ravines and fences in places where they no longer wanted this to happen and rerouted traffic to a few points.
Canada has closed its border with the U.S., last I heard. We have apparently closed our border with them. I think we both allow essential workers, but there's red tape. Family visits too.
Mexico has likewise closed to the U.S. (and so far, has a much lower rate of virus, many factors). And we have closed to them - obviously and have more border patrol than ever before. But there's still significant essential traffic.
At any rate, the vast majority of Americans can only travel among the states, which is why it's a concern at that level.
Arizona actually was quarantining incoming people from certain states (unsupervised though, I think - unlike Hawaii, which of course has the lowest per capita rate in our union - and they will continue to quarantine people - supervised, criminal charges possible - for quite some time to come).
That means, in theory, as a Californian, if AZ has border checks, I can only go to Oregon and Nevada, and then to Washington and Utah/New Mexico beyond.
At this point, for a vacation (camping), I'd feel way happier in New Mexico.
