@ashs till the day your visa status is changed to permanent resident, in the eyes of both China ( I assume ) and the USA you are a temporary resident/ Non-Resident Alien. Thus the article 20(c) still applies but one would think that once you have applied (i.e. taken steps ) you have decided/ declared your intention to settle down in the USA and thus probably violated the requirements/intents of article 20(c) -- which assumes that you are in the USA temporarily. That IMHO -- others may disagree.
BTW -- I have confirmed that there is no totalization agreement between US & China and thus my comments about FICA stands as is.
Good Luck
