I seriously doubt that Russian troops would choose to engage US troops, thereby provoking a major conflagration.
If they actually did so, the (attacked) American troops would have no real choice but to respond with the utmost force...
Neocons are so silly. Provoking a war with Russia to help cover zero? In fact, a war might just salvage zero and his fellow communists chances in november. If you are old enough to recall how the US behaved when soviet soldiers were in central America, you may understand.
Actually, my quote was about US Forces opposing the Russian Army...which is FAR less likely than Russian forces opposing the US Army...in Ukraine.
The geopolitics of this matters. If the Russians moved on Kiev (unknown at this time), they would likely not shy from encircling US Troops in Ukraine and escorting them back over the border.