ShawtyCat, I don't know that there is a short, easy explanation of what American cuisine is. Trying to define American cuisine by Hot Dogs, Hamburgers, and french fries is like trying to define chinese food by Egg Foo Young and Chow Mein, or Mexican food by burritos and tacos or German food by Potatoes and sausage.
America is a very large country, with many different cultures living in many different geographical and metorilogical areas. To try and define such a diverse collection of foods and cultures into a few simple statements would be next to impossible. But let me try and make some sense of it.
On one hand, your assumption that American cuisine is "Fast Food" is correct. Americans have come to love speed and convience, and much of our food has grown to reflect that. Fast food joints and chain restaurants have sprung up around the country catering to people who really don't care about the food they consume or are looking for something familar. To many Americans, knowing that they can walk into a McD's anyplace in the country and order a Big Mac is very comforting. It is also mindless, another thing many Americans appreciate. But this is only one level of something complex. This is the most superfical, yet most widely recognized form of cuisine this country has to offer.
To really understand American cuisine you must understand that it is all about regions, just like in France, Italy, Germany, Greece, and many other countries. Each region appealed to different types of settlers (immigrants) and had different native foodstuffs to offer. When I think about the regional cuisine of the US I usually divide it into 6 catagories (each one can be broken down further, and some people might argue how I divide it, but for the sake of keeping it simple let's keep it at 6). These regions would be New England (NorthEast), the South, the Midwest, the Southwest, California, and the Northwest. Each of these general areas have lots of things in common such as cooking techniques, native ingredients preferences for one type of starch over another, etc. Again a lot has to do with the immigrants who came to that area, and what they found when they arrived. It is these cuisines that grew up in these areas that are basis for American cuisine. As people traveled across the country foods were exchanged and these regional boundaries go more and more blurred. Add to this modern travel, and immigrants coming from different parts of the world and things really start to get complicated as new foods continue to be introduced.
After re-reading what I have just written, it all seems so esoteric, and I am not sure I have really answered your question. I don't know if that is really possible without getting into a long discussion about each region and the foods that grew up there. I will try and make some very broad statements about American cuisine, but these can only be statements that are very generalized, in the broadest sense of the term.
-Americans tend to eat more meat based proteins that most other countries. We like large portions of meat and fish.
-As a general rule, Americans prefer potatoes as a starch, over rice, except in certain areas.
-Americans love carbs (breads,cookies, and such things)
-We also tend to use lots of sugar and salt in our foods
-American cuisine tends to be more fluid than other cuisines that that been around much longer. It tends to adapt more quickly to influences from other parts of the world.
Beyond those few statements, I am at a loss at how to define American cuisine without taking up megabites of space.