Lets think about it, the United States, the big imperialistic power of the 21st century. Our government gets away with pretty much anything they want within our borders. We can imprison anyone for anything rather they are guilty or not. I would say that is an example of imperialism at its finest. The strong overpowering the weak. When Herald and Kumar board the plane they are just innocent people on a flight to Amsterdam. When Kumar lights his new bong on the plane in the bathroom, air officers think it is a bomb and have them locked up immediately. Upon being sent to Guantanamo Bay they are forced to do things to cops at the prison. No one believes that they were just smoking a bong. They automatically assume that it was a bomb based on their ethnicity and the US flexes its muscles by detaining them under false ideas.Another time in the movie where imperialism is a underlying idea is near the end of the story. Herald and Kumar find their friends fiance that they thought would help them out of their precarious situation between them and the government. The fiance said he would take care of it and sets up a meeting with some people who can get them discharged from their charges. When they show up its a completely different story. The people who are supposed to help them turns out to be using help as a cover to arrest them and send them back to prison. The friend they thought they could trust to help them turns their back and helps the strong overtake the weak who are Herald and Kumar.
Overall I think there are better examples of movies with imperialistic themes but this one was the first to come into my mind, and it was one of my favorite funny movies of all time.
Image source : http://movierule.wordpress.com/2008/06/03/harold-kumar-escape-from-guantanamo-bay-movie2008/