Will my HTC Wildfire (sold in Europe) work in the US? Is there a specific carrier I should use?
Unless your phone is SIM locked it should work with any GSM service within the US.
I think you can't. see availability on wiki page:
Wildfire : http://en.wikipedia.org/wiki/HTC_Wildfire
Wildfire S : http://en.wikipedia.org/wiki/HTC_Wildfire_S