Will I ever be seen as "one of us" by the classmates or will I always be looked at as the amercan exchange student.
I think that it depends on the particular group of people and it you are a friendly chap and the class is a friendly group of people, you will be all right.
Fitting in at all costs is probably not the way to go about it. be yourself and don't try to compromise your own American values in order to fit in. You also have something to offer to them. I would look at it from that point of view:).
Forum posters are not the reflection of the Polish society. If you are interested in your Polish heritage then taht will be the opportunity for you to experience it and compare the reality with what people write on forums:)
Good luck and enjoy yourself:)