Hi,
Does anyone know of any US broker that has index pairs like USD index and GBP Index to trade?
Hi Boxer,
Welcome to BabyPips 
CFTC regulations prohibit forex brokers from offering currency indices (or stock indices for that matter). However, FXCM offers a solution for US traders with our currency baskets for USD, GBP, EUR, JPY and AUD, as well as baskets designed to take advantage of interest rate differentials.
Note that for non-US residents, FXCM also offers trading in the Dow Jones FXCM Dollar Index (ticker: USDOLLAR).