I've been to everywhere on your poll apart from Miami and Hawaii. I've also been to a lot of other places in the US you haven't mentioned. Thinking about it, as I'm only 21 I'm pretty darn well travelled.
My favourite place in America? I can't say. It really depends on your mood and what you want. I LOVED San Francisco, the city is just so different from a normal city, with such amazing scenery. It's a shame its so far away from the UK, if it was a shorter flight I would go back there as much as possible.
Florida is perfect if you want the typical tourist holiday. The parks are down right amazing, and so much fun. The weather is glorious and you always have stuff to do.
Vegas, for me wasn't that great, it's an amazing place but unless your going to gamble there's not a great deal to do there for more than a few days, and I spent a week there - death valley is close though and that is worth seeing, just so you can say you know what it feels like to be melted alive.
New York is, well New York. I don't think I could say anything more about it, apart from you need to go there. I work in London and it was amazing to see the contrast between the two. My only issue was that I spent nowhere near enough time there, and that I must go back and stay longer next time.
Yellowstone is stunning. The whole area is magnificent. The park hotels are a rip off, expensive and small - but they have a monopoly so if you want to stay you have to grudge and bear it. Is a place you need to visit if you love to see what nature is capable of at its most extreme. Lake Tahoe is also only a day or so drive away, and is such an amazingly beautiful place, the combination of the two is just stunning.
I have been to most of the typical tourist places in America, and quite a few not. There aren't many places that come to mind that I have yet to see, however there aren't any I can think of that I would not happily re-visit.