My advise is to enter a university in your country, and from your university, apply to a study abroad program that another university offers. You can do that!
If you do it that way, your time abroad will most likely not count directly back for college credit, but you're not doing it for the credit right?
Also check this I just saw.
http://www.usservas.org/about.html Also, the first time I went to Japan I was an exchange student thru YFU, Youth for Understanding International Exchange. See if you can find anything about them online.
I highly recommend going to college though.
Also, try asking on the discussion boards on my site if you haven't already. Maybe you can get some new info too.
Most of the young people I meet in Japan though (hey, I'm 25 I'm young too) are either in college on exchange, or have just finished college and come to teach English. There are also many universities that do Internships in Japan.
I know quite a few French people who came over doing internships sponsored by their school!