Can I become a foreign language teacher? This is my story. (Or will be my story - I'm only 15)?

You didn't really need to write all that down. To be a foreign language teacher in the US you need a BA degree in the language and a teaching credential in which you specialized in language teaching. The GED-community college-finish at a 4 year college is a perfectly acceptable route. There are also some 4 year colleges that will admit you on the basis of a GED. Your overseas experience will help you with your language skills and will look interesting on your resume.