It doesn't matter since the OP is arriving on an international flight. At SFO (and most US airports), even if the bag is tagged all the way through, it must be picked up at the first US point-of-entry. Typically, with a normal layover, one would drop at the bag re-check after customs, but there is no requirement to do so - there is nothing preventing someone with a bag that is tagged through from walking by bag re-check and not checking it.

IAH is different, if you are transiting but going directly from an international flight to a different international flight, you don't have to pick up the bags. This is pretty uncommon in the US.