I travel to the US about 4 or 5 times a year and I have found the Indian Restaurants there diverse from each other quite a bit. The ones that are run by "Southern Indians" I have found there food to be more like Indian traditional home cooking, their Madras's contain a lot of coconut and curry leaves, but the the ones run by "Northern Indians" are much more like our restaurants.
One of the best I have eaten in is the Gaylord in Schaumberg which is not far from O'Hare airport in Chicago.
http://www.gaylordil.com/ In fact the last time I went there which was last September, there was actually an Indian from Glasgow working in there.
I'm off to Florida on Tuesday and am actually attending a cooking class in the Green Chilli in St. Petersberg. It was only $40 with a voucher I found on line so am looking forward to this. I'll let you know how it goes and also whether it is Southern Indian or Northern
