Default [Q] USA at&t service question - noob to this android world

I have recently bought a NIB factory unlocked S4 gt-i9505. I have rooted the phone and customized.
(Just info in case its needed or changes things)

I am currently in Romania, but i need to know if this phone will work on at&t network in the USA with full coverage (lte,4g,)

Any feedback about this is very much appreciated.