must have sponsorship

Only US gov authorized companies, big companies usually, can sponsor the your application to OPM. Depends on the level you apply, it requires US citizenship and years of residency plus a clean history. Probably a couple of young Chinese foreigner (NOT ABC) if not at all can pass TS/life-time polygraph/SSI. If you have oversea relatives and maintain regular contact with them, then you are out luck. Myself had waited 3yrs and appealed for it, even though my parent are US citizens, my in-laws are not. And that is only for DoD secret clearance. After all the trouble I won't dare to go for TS, which may turn your life upside down due to intensive investigations. However it's well worth it. Clearance mean $$$$$, pure and simple.