If it is a Javelin, does that mean US Troops might be on the ground
or the US has supplied a few to the rebels ?????
US troops on the ground fighting for the Assad side?
Not likely. IIRC, that video is a shot of a rebel group in action with a tank.
Various gear of war has been infiltrating into Syria via a few of our allies in the Persian Gulf for the past few years, to support various insurgent factions.
They have plenty of American kit that might get slipped across a border here and there ...