Will the Sony Ericsson P1i work in the U.S?

Ya sure your sony ericsson P1i mobile will freely work with t-mobile sim in US only if the phone is unlocked one else if the phone is locked to some other network provider in other countries then it wont accept t-mobile sim until you unlock it .You can easily unlock your phone using sites like Unlock-Zone.com here they are rendering network unlock code for all mobile models at reliable cost .You first verify that whether the code is available for your country and network provider .If yes then pay for it and unlock your phone then freely use it with any GSM sim ...