I'm not sold on Nokia being a game changer in the US. Why? Because only tech nerds are talking about Nokia and how it MAY be a game changer. When is the last time most non-techie Americans have seen a Nokia phone in their local AT&T, Sprint, Verizon or T Mob store? When is the last time most non-techie American's interested in smartphones associated Nokia with smartphones? Nokia is so far removed from the buying thought process of non-techie Americans. Nokia has to re-establish itself on American soil before non-tech nerds go crazy over the "sexy" Nokia hardware.
The reason Nokia has flopped so badly in the USA is because they sold almost all their phones unlocked. You can't go into a Verizon or Sprint store and pick one up. The only store I've even seen them in is Fry's, and it was a really pathetic unmanned display, separate from their other smartphones, with non-working models. In the USA, very few people buy their smartphones unlocked.
Nokia has already said that they are taking a very US-centric approach to their WP7 handsets. They will be selling them subsidized through carriers. I'm baffled that they waited so long to start doing it this way. The most recent rumor is that they're working on mid-range devices on T-Mobile and AT&T, and a high-end device for Verizon.
Also, MS and Nokia supposedly have money set aside for a huge advertising blitz. Nokia's hardware is some of the best, sexiest hardware out there. In fact, IMO they're the only ones who can do it as good as Apple. If they advertise well, I believe they will sell like crazy.