Biden is a lame duck president with NO PUBLIC MANDATE and subterranean approval rating, he got ousted by his own party before the election for being mentally incapacitated, his defense against a Justice Department inquiry is he's too old and senile, his party just got BTFO in a national election. No NATO or NATO proxies have ever launched long range missiles into Russia in living memory. How is this guy 
fit for office
STOP EATING CRAYONS AND DO YOUR FUCKING JERB. "Senile old man sends young people to WW3 out of spite"
They could say anything is a red line. They could say sanctions are a red line, they could say supplying Ukrainians with tanks is a red line. Ultimately they're going to be fine.
Deploying NATO-member troops into Ukraine to fight directly, or anything else that involves a direct conflict, is an act of war, because that is what is consequential. Arms dealing has been going on since before the SMO started, it's a difference of degree rather than category. Whining about it is a fuss over no substantial change, and over a type of weapon that is not new to the conflict.
The whole Ukraine war is happening because people in charge of NATO thought that Russia's stated red lines could be crossed over without concequence. And the American empire has already been dealt a fatal blow in retaliation, with American hegemony in active collapse.
The accelerationist part of me rejoices seeing how idiot westerners will lead us to WW3 and destroy themselves. The realist part of me is terrified of WW3. How conflicting these feelings are.
American global presence is still going to take decades to fully wane, unless the process is precipitated all at once in a widely encompassing outbreak of conflict. Beyond a horizon of 2 years into the future, I'm not sure which I prefer either.