I can count 10 Chinese take out places in my home town off the top of my head, but only a couple of other cuisines. Why is this?
Edit: I'm talking either delivery or pick up. Not fast food chains. And I live in NE Ohio but I've been around the country and there never seems to be a lack of Chinese places to call for food. So I'm basing this a lot on personal experience.
Edit 2: So maybe calling Chinese food America's #1 ethnic take out food wasn't accurate. But still to me at least there still seem to be a ton of Chinese restaurants that all do take out and many deliver, while other ethnic foods are harder to come by. So I guess my question is how did Chinese food get to be so big in the US when other ethnic groups make up a much higher percent of the population. I'd have to search to find Mexican food that delivered, but I can take my pick of Chinese places.
First, I'm not sure we can definitively say Chinese food is the #1 take-out in the United States. Putting that aside, it's been a while since I've studied this topic so I'm not comfortable giving a detailed top-level answer. What I can do is suggest you read some publications from my old Professor, Yong Chen. He actually specializes in the history of Chinese food in the United States. In particular, his book Chop Suey, USA discusses the evolution of Chinese-American food.
With all due respect to the question, are we not considering pizza to be "ethnic" food? It's certainly arguable that it's American and "non-ethnic," since we haven't defined what that means, but you do mention "Italian" in your question, and I would have to believe that pizza is the #1 take-out/delivery food in the U.S.