America is huge, just vast, I visited 6 states in 2 weeks last year (all of New England) albeit briefly, and we were hardly off the road to do that, the mileages were massive. And that is just one tiny corner of the USA, a tiny, tiny percentage.
I think the place is just so big and so diverse that it really is unmanageable, it’s easy to see why these mentally ill people fall off the radar, and why ‘the state’ can’t keep tabs on everyone.
Their gun laws are questionable, obviously, but as for everything else, it just seems nigh on impossible.