Actually, German food is not that much different from the daily food in the states. Breakfast in cheaper hotels can actually really just be bread, bread roles, jam, honey, cheese, ham/salami... and boiled eggs, but usually they also offer müsli/cereal, joghurt, fruit/fruit salad, juices.
You should try the different varieties of bread available in Germany. They are very different from what is offered in the states.
Lunch is usually the main meal of the day (traditionally), but more and more people are switching over to having the main meal of the day in the evening, since they than have time for cooking at home.
There are less fast-food chains in Germany than in the US, the main ones being, of course, McDonalds and Burger King. Starbucks and starbucks-like stores are baically on every corner, and new Subway-restaurants are shooting out of the ground like crazy.
You should not miss out o the favorite "German" fast food, the "Döner". IT is actually Turkish food, but very, very popular in Germany. It is flat white bread, cut open to form a kind of bag, which is filled up with crispy meat strips cut from a huge revolving spit, salads, "Krautsalat" (cabbage salad, usually with white cabbage, but if the shop you go to offer it, try having it with red cabbage salad. Not every sho has it, but it's delicious!), tomato slices, joghurt sauce and, if you want to, they or you can spice it up with a pickled green pepper and/or powdered chili. A Döner should cost at least 2,50€ (to guarantee good quality, or that's what the consumer whatevers says, anyhow, and you should see, or be able to be told, what kind of meat it is they will give you (from veal to turkey - everything is possible)
Ice cream is also different from American ice cream, as well as chocolates. Sodas tend to not be as sweet as the American versions (yes, even coke and pepsi). Also, we do not have every American soda, but therefore different ones, like Fanta and Shweppes.
It is also sometimes a shock to foreign people that sweet main courses are nothing unusual in Germany. Sienna O. said, for example, Kaiserschmarren was a dessert. It is not. It is a main course which comes traditionally from Austria, but is quite popular in Germany. Other sweet main courses are, for instance, "Dampfnudel", a big steamed yeast dough dumpling, filled with some fruit, traditionally with plum jam/compot, served with vanilla sauce and a mix of cracked poppy seed and powdered sugar; "Arme Ritter" or "Rostige Ritter" (poor knight/rusty knight), which is basically the same as french toast, only that the rusty knight usually is a bread roll. Milchreis (milky rice = round rice cooked in milk), Griesbrei (seminola cooked in milk). All of those are served with fruit compot.
Rick w suggested to try russina sekt. But there are numerous german wine regions, and numerous German Sekts, so if you have the chance, visit some wineries (the Mosel-Region is one that has not only very good wines, but is also absurdly pretty! As well as lower Frankonia in northern Bavaria (area around Würzburg), and of course the whole Rhine-Region and Nahe-Area).
Germany also has a whole lot of very different beeres to try. Weizenbier of course is great, but have you ever tried a "Kristal-Weizen"? It is a filtered Wheatbeer, and unknown in the states. If you try it, don't be surprised to find half a slice of lemon in your glass. Yep, it's supposed to be there! "Köstritzer" is a very good black beer, and german breweries are producing endless supplies of "Pilsner" for every taste.
Popular are so called "Biermixgetränke". Mostly they consits of a Pilsner-kind beer mixed with lemon/coke/grapefruit... lemonades. Köstritzer also offers a mixed version, called "bebop".
You might also want to try "Bionade" ("coffee fellows" coffee shops, among numerous others, offer it), which is organic lemonade in interesting tastes, and has very low sugar.
Oh, and one more thing to rick w.: "Kümmerling" is not a Kümmel-liquor (cumin), but an herb-liquer. A true cumin-liquer would be "Küstennebel".
OK, that is all I can think of right now. Don't be afraid, you'll find loads of stuff to eat that you will liely miss when you get back to the states.
Have fun in Germany!