At the same time, I think it's pretty clear that a no fly zone could have been done with few American casualties, and Putin would still have no ability to respond because they physically cannot. Putin, and more importantly all the rich assholes under him who like being rich assholes, don't like the idea of being rich assholes in a post nuclear exchange Russia, will likely not hit the button. Add to that the likelihood that most of the Nukes would not go off, or blow up on the launch pad even (Most of Russia's nukes are liquid fueled ICBMs, which are terrible in terms of staying reliable for cheap, and Russia spends less on it's entire military than the US spends on just it's solid fueled missiles). Russia has had at least one nuclear test fail since the war started.
We have been holding back equipment because "what if we need it" (to fight who?), or "but they'll retaliate!" (with the one tank they could afford to spare for the parade?) or "but it costs so much money" (only when you calculate it with the price we paid in 1980 instead of the negative value these old machines that need to be sold or decommissioned currently have) or "We can't send cluster munitions because the UXO risk!" while every day Russia is still in Ukrainian territory is actual Russians purposely shooting at Ukrainians and RUSSIANS HAVE LITERALLY USED CLUSTER MUNITIONS ON CIVILIAN POPULATIONS!
The actual insanity is sending Ukraine 100 Bradleys instead of 500 and then bitching when their offensive is mediocre.