Problem here is that when most people think foreign food, they think of the delicious takeaways situated in their own country which offer substandard alternatives to their own nation's genuine dishes. The Chinese are not big fans of Sweet and Sour. Indians do not think much of curries (being a British invention and all).
Most people dislike a lot of authentic Chinese food (dim sum seems exclusively made up of tripe, stomach lining, chicken feet, and boiled bread), so the Chinese have discovered what is popular over here, and sell that instead. When a chinese person goes into a take away, they are usually handed a seperate Chinese menu with dishes more familiar to their tastes (the food is often better on these).
Saying all that, I love my pseudo-mexican/indian/Italian/Chinese foods.