If you watch a lot of older TV, it was almost always portrayed as Caucasian suburban nuclear families. The soccer mom making casserole for dinner, the business dad, the skateboarding son with an apathetic attitude.
IRL tho, especially lately, it really depends on where you live. So there's so much cultural overlap these days. A lot of it has to do with location - when I lived in California, a lot of my friends were Mexican. Michigan, I actually met a lot of people from Africa, which actually really changed my perspective on the continent, and man, if you think the south has good hospitality, you'd be amazed at how kind people from other countries can be. Florida was kind of a mix, a lot of people from Latin America countries (and soooooo much good food). Here in CT, a lot of people from India. It's such a melting pot.
I think "American" is more of an idea or an attitude than a look. And I'm not talking about the one that foreign media portrays us as, as cowboys or the negative military image we sometimes look like in some countries...I'm talking about people helping each other, doing good work, chasing your dreams, working to be successful even if you're a late bloomer, stuff like that. I know people who have only been immigrants for a year who are more American than people who have lived here their whole lives, so I don't think there's so much of a true American look as there is the way you live your life.