Ekk: Have you heard of the expression "You are as American as LEMON PIE"? It means that you came here from another country, but you now THINK. ACT, and SPEAK like a native-born American. It is a very high compliment!

maybe american pancakes.

I'm not sure there is a "most common" pastry in America. America doesn't really have much in the way of traditional foods. It really just depends on what individual people like. Coffee shops serve muffins a lot, so that is popular. In bakeries, you'll see donuts, danishes, coffee cake. My personal favorite is cake donuts. :)

I often help a friend of mine who owns a "Pastry Shop". She sells bear claws, fruit filled Danish, strudel, scones, croissants, and other items I usually consider as pastries. Often, people from the Indian subcontinent see the sign for the shop and come in expecting to purchase fruit filled cake slices. There were so many of these requests, that my friend now bakes layer cakes that she frosts and includes strawberries, pineapple, and other fruit and they are sold by the slice as "pastries". Her palmiers, especially the ones she makes with cinnamon sugar and walnuts are very popular. The only "doughnuts" she sells are fried Ghanaian ones.

Off of the top of my head, I'd say donuts, but I haven't googled to check. Certain brands are nationally famous and have their own chain of stores, like Dunkin' Donuts and Krispy Kreme.