That the studios realized there is easy money in direct-to-video-sequels to popular movies is a development that can be witnessed with franchises like American Pie for quite a while. Also with Road Trip from 2000 the studios saw potential for a sequel. That the only common ground between the movies is the character Kyle and the college in Ithaca should not be too much of a surprise. Fortunately, this exemplar of the old and recently tiring student-drinking-party-sub-genre is not a total failure and is at least entertaining until the end even though it is not exactly intellectually challenging, of course.

Besides that, there is the usual release-policy. An R-Rated version for the US stores that do not want to sell Unrated versions and an Unrated version for the others.
While this was a pure marketing-scam with the first movie this version does not contain great changes, either. A completely irrelevant plot scene and a bit nudity, but that is it.

Comparison between the Unrated-DVD and the R-Rated-DVD (both from Paramount).

3 changes, being
1 extended scene using alternative footage
2 additional scenes

The Unrated version is 87.44 seconds or approximately 1 minute 28 seconds longer than the R-Rated version.

Additional scene
0:21:35: Andy and his buddies go to Katy's room. After Andy knocked on the door Katy is standing there (still pretty modest) in a nightdress, but as we can see on the look of her face she is not very happy that Andy brought his friends. He goes into her room and tells her that they have to go see a sponsor before he can come to her and they can celebrate their anniversary. She is not thrilled about it but accepts it. For encouragement Andy tells her that he wrote a song for her and as soon as the door has been reopened his pals burst in and start imitating him.
79.16 sec.

Alternative footage
R-Rated: 25:58
Unrated: 27:02: Both versions show the ladies having a pillow fight in the bus. The R-Rated version remains at its height while the Unrated version pans down from time to time to show the hairless private areas and naked bottoms. (Here only the images from the Unrated version)
The Unrated version is 3.2 sec. longer

Additional scene
0:27:15: Once again, the naked ladies can be seen at their pillow fight, then the image freezes and the next scene is being shown.
5.08 sec.