After thinking about it, I should probably expound a little bit.
There are a few big differences. As I said above, where I was at (Mumbai, Gujarat, Rajastan, Delhi), I don’t recall running into anything that was just generic “curry.” Of the “generic Indian restaurant” dishes I did see, like murg makhani/korma/tikka (not tikka masala), the one that was the most different to me was the vindaloo. Vindaloo is traditionally made from pork, which I was aware of, but the version of vindaloo I was served was a good bit tangier and less spicy than what I’ve had here in the US and in the UK. It was also less heavily spiced. It didn’t have your typical Indian “curry” flavor and really felt more like a Portuguese dish with Indian influences, rather than the other way around.
Dishes like palak/saag paneer, methi mutter, roghan josh, aloo gobi, chana masala, didn’t taste all that different than what I can pick up on Devon St. (the Indian district) here in Chicago.
Also, at least in the areas I was at, naan was not heavily consumed at all, but chapatis/rotis or similar flatbreads were more typically ordered, and food was generally eaten with hands, using the rotis to scoop up the pieces. That said, at the restaurants I generally visit in Chicago, it’s similar.
Now, remember, India is a HUGE country, so to speak of “Indian food” and “Indian restaurants” in general is a bit problematic. I am speaking of my experiences and impressions, as an American, mostly in Gujarat and Rajasthan, and my familiarity with Indian food in America is in Chicago, where there is a big Indian community, and specifically with food from those regions where I travelled.