...because all of Europe has been pissing and shitting themselves as an unofficial coalition to contain Russia's rejection of NATO encroachment. They've been draining US coffers to bring missiles closer and closer to Russian borders in order to reduce their reaction time to near-zero and exert pressure to get them to 'play ball'. Without US backing, Europe would not be able to contain this. The US is laundering its status as Power #1 to flex on Power #2 and it's past the tipping point. You're not wrong that Russia is significantly disadvantaged, but to quote Biden, "C'mon, man!"
The UN Security Council would have you believe that the U.S., Russia, China, UK, and France are equals. Do you really think France is equal to Russia? France has 200 nuclear warheads. Russia has ~5800. Nukes are rapidly becoming irrelevant but they still matter and are roughly reflective of political clout.