All the online movie seller/renter that I am aware of are geolocalized because of film rights. So it's likely you will not be able to see in the US the films you bought in Germany. A solution could be to use a US proxy while in germany to create a US account for these services. Another solution would be to buy US DVDs or BluRays in Germany (there are shops with an import section) providing you have a multizone player or use your laptop (TV should not be an issue unless it's very cheap or very old).
The simplest legal solution would be to find a rental store or an online pay per view site and just pay some money to watch film and not own them until May.