If you're a billionaire or close to it, the US healthcare system is fantastic, unless of course you're traveling in one of the "medical deserts" and have an acute emergency.
You'd still stuck with the built environment as it is, just as everybody else.
A billion is just three Manhattan skyscrapers, so it can't change a city. Depending on where you live, you might well experience the exhaust, dust and noise of these environments, no matter how luxurious your individual dwelling.
I think that's more a problem with being famous: the top of the Wikipedia list* as I write this is "Bernard Arnault & family", who I've never heard of and therefore couldn't spot in a lineup much less a crowd.
But I did double-take when walking past Russell T Davis (or a lookalike) in Sheffield a decade and a half ago, and Richard Osman in Cambridge train station some other time.