We supply the Touch factory unlocked and SIM free, so this is no issue.
The mains adapter is a UK 3 pin plug but is 100v~240V, so all you will need is a travel-adapter to convert to US socket, or simply buy a cheap and cheerful universal MiniUSB charger.
The data side of the Touch is not 3G, but EDGE/GPRS.
A quick search comes up with these network carriers as offering EDGE connectivity in the United States.
http://en.wikipedia.org/wiki/Enhanced_Data_Rates_for_GSM_Evolution#Americas
The HTC Touch uses the following spec EDGE connectivity: GSM/GPRS/EDGE Tri-band 900/1800/1900Mhz. EGPRS Functionality - class B, Multi-slot class 10.
A quick (or long!) phone call to your preferred carrier would confirm this is ok for use with them.
Regards
Ivan