If you're using your school's network to connect to the Internet, chances are you will not be able to use any outside ISPs, since they usually do not allow them. I would check with your school first to see if they will allow you to subscribe to other Internet Providers.
Why do you need it to show your IP address being in the united states?
Regardless.. You're gonna need to rent out a VPS.. or dedicated server.. or even send a machine out to be colocated on an american network, and from there you can setup proxy server like squid on that server, then configure your home software to make connections through that proxy, thus making your users believe you are really connected on whatever network your server is hooked up to.
this isn't really changing your ip.. you'll need to be master of your own network for that.. you might be able to contact your ISP (your college) and get them to setup some kinda system.. but i don't think they could make you appear as if you are in america.