Your first point is a big one - the US has an incredible variety of places to visit. I'm from the UK, and while there are some amazing places to visit in the UK, there is a lot less variety than there is in the US. I spend 10 days driving from Denver to Vegas and saw far more scenery than I ever have in the UK. If I lived in the US I could easily imagine not leaving it for years (when I lived in the UK I'd go abroad at least twice a year).