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.
Uh, why might you suppose that US troops are so docile as to allow themselves to be "escort[ed]...back over the border," ever so meekly?