Consider this: Russia threatened "escalation" and promised attacks on NATO allies if we sent M1A1 tanks. We did, and nothing about their approach fundamentally changed. They made the same threats with HIMARs rocket launchers; again, we did, nothing changed. The Patriot Air Defense system, the cluster munitions, the F-16 fighter jets — over and over and over Ukraine has asked for support that the Biden administration has balked on giving immediately, all while Russia said "if you do this, we are really going to make you pay" — then we eventually do it and Russia doesn’t change its strategy.
Is it risky to bet that Russia will continue to bluff? Of course. Do I think Russia has any interest in widening this war — including a nuclear escalation — beyond the territories in Eastern Ukraine it is now struggling to defend or capture? No. NATO involvement would be a death-knell for Putin's war, and he knows that. Instead, after 1,000 days, the U.S. should start acting confidently, with the understanding that Putin is doing more flexing than punching.
It’s possible that threats exist I don’t fully understand. But with 20/20 hindsight, if I could go back to the first week of this war, I think I would have advocated that the U.S. give Ukraine everything it wanted right away and allowed them to better defend themselves — within their borders, in the skies, and on Russian territory. What we've done instead is create exactly the kind of war of attrition Russia is built to win, spent exorbitant amounts of money on weapons, and allowed a million Ukrainians and Russians to die.