Since you mentioned North America, I can only speak for the US...
Correct me if I'm wrong Canadians... Rogers only uses 850mhz 3G right? No 1900?
If you bring it to the US and use it with AT&T I'm pretty sure you will be able to use 3G on the N97 on places with 1900mhz 3G..
Such as Major Cities like NY, CHI, LA, etc..
Also AT&T's 3G is HSDPA so you will be able to utilize that as well on the N97..