Compare the menu at Deny's with that of any large German restaurant chain. Some things are similar, many are not.
Looking at the Denny's menu, with the exception of a couple of the soups and some of the deep fried dishes, most everything else would be common in Germany (with different names, and usually a wider selection of cheeses).
How's about we compare it with what's actually served in traditional homes and restaurants in Germany, rather than what is served in German chains across the ocean?
After all, what's served in Chinese restaurants in the US bears little resemblance to what's actually eaten in China. What's served in Indian restaurants in the US bears little resemblance to what's actually eaten in India. The same is true of German restaurants in the US - they typically serve what Americans *think* the Germans eat all the time, whether or not that dish is commonly served in Germany.
I was talking to an Indian friend of mine once about Indian food in restaurants here. He called it "wedding food" - stuff that is laid out at weddings because it's cheap and tasty, not what would be served in a home or family restaurant in India.
I was eating at Mader's in Milwaukee a few years back, and ordered the Leberknoedelsuppe as an appetizer. After eating it, I was asked by the waitress how I liked it and I told her it tasted just like my mom's. She said that it was her recipe (because the cook didn't know how to make it "properly") and after a bit of discussion, it turns out that she grew up near my mother, just outside of Graz. I ordered the Franconian Chicken Schnitzel for dinner (Chicken breast sauteed with onions, mushrooms, chopped tomatoes and garlic, simmered in Madeira wine veloute sauce. Served with spaetzle and julienne vegetables). Typical German dish, and would be common throughout the US as well - they make something similar at Appleby's, for example. It's called the "Smothered Grilled Chicken" served with mashed potatoes instead of noodles (Spaetzle are egg noodles).
