The frequency stuff does suck, but it'd be easy for Nokia to release the same phones with a different radio inside (or even the same radio, just firmware modified to have it operate on different frequencies.) I believe they all use the same antenna types.
People think the "razr" is the best because it came out, was really thin, and looked "sleek" to most people. It was aggressively marketed, it's available relatively inexpensively now, and it works. It's not the best by a large margin, it's got tons of flaws, but it sells.
It also has very little/if any competition. Looked at the rest of the crappy phones we have over here? If Nokia got serious and started aggressively attacking the US market, providing GOOD phones that supported the US frequencies (really not that hard, and not requiring an expensive retooling) - they'd easily pick up good market share. A good deal with T-Mobile as a carrier would help them immensely too, maybe when T-Mobile starts rolling out the 3G stuff Nokia will hop on board with great phones that support US 3G+ standards. Talk about an instant leg-up on the competition!
Nokia has been everything but aggressive in the US market, they've all but ignored it. That's why you don't see high end Nokia phones around here. There's PLENTY of gadget heads who'll shell out the money, look at all of us importing phones that doesn't even work fully (broken 3G/etc) in the US.