"large majorities of americans support a no-fly zone in Ukraine"
This is an unspeakably bad idea. It vastly increases the chances for WW3. Pretty sure Biden knows this. But man democracy sure is stupid if you have a country that thinks this
I am not sure if it increases or decreases the chances for WW3. While doing it would be technically joining a conflict NATO is not already in (which is bad), it is not really an escalation relative to what Russia is already doing to Ukraine, and it does signal a willingness to use strength in response to Russia's escalations (which is good, and a lack thereof could have disastrous consequences).
Also, from what I'm gathering, the Russian army seems to be in a weaker state than I had initially thought — the invading troops which are currently not doing super impressively against Ukraine, while few in number relative to the Ukrainian forces, nonetheless appear to be a very significant % of Russia's ground forces, almost certainly more than half of them. There's e.g. evidence of troops from military bases near the Finnish border fighting in Ukraine. I didn't originally realize their ground forces were that small, but apparently that's how it is. They've already lost a bunch of expensive equipment and a substantial number of soldiers. I don't think Russia has the resources to attack any other country as long as the Ukraine war is ongoing, and they have never dared to attack NATO.
I have tentatively been leaning towards supporting the no-fly zone in Ukraine.