I'm in Australia and here you can still get into university if you haven't finished high school.
If you can't get in by sitting the STAT test you can go to a TAFE college and start doing any course, then if you go well you can get into uni and sometimes skip first year.
Isn't there some way for you to get into an American university like that? Then if you have an American Uni degree you can get a job in Japan or do university in Japan or even a university exchange.
Otherwise, come to Australia as an international student.
They'll let anyone in if you pay up front!