Most of the mobiles in India work only up to 3G in USA. 4G used in India is TD (Time Division) where as in USA it FD (Frequency Division) as of now. It is possible that In dian carriers accomodate TD in near future (Jio has already taken license). It is matter of government policies and adaptation of technologies.
For frequencies used in USA check the figure below:
(http://certforumz.com/index.php?action=dlattach;topic=1870.0;attach=4183)