Motorola Mot G 2nd Gen - does it work in the US?

[AC Question]

I bought a Motorola Mot G 2nd Gen from amazon.co.uk and have put one micro sim card in from Giffgaff, the other slot is empty.

I am just about to travel to the US for work and was wondering if my phone would work there? I've been looking online and I've not found a definitive answer. Would I need to unlock it?

 

[B. Diddy]

Welcome to Android Central! Is it the XT1068? I assume so, since that's listed on Wikipedia as the dual SIM version from the UK. It should work on either T-Mobile or AT&T.