I'd have to read the actual assurances offered to answer definitively, but it seems we agreed to protect them from Russia by published accounts. I will welcome correction on this.
From that perspective, I get why Conor thinks we should fight. But, absent a moral obligation, I suppose I hope we stay out of it...we should not be trying to fight in every war, and Ukraine has far less worth to US interests than a country like Taiwan.
Ukraine was naive to trust us. But, they were new to global politics.
We shouldn't have given assurances we would never honor...in the name of non-proliferation, a policy goal which we would abandon soon thereafter. (Chris won't want me to mention that Clinton made the assurances, Clinton & Obama abandoned non-proliferation with their treatment of N.Korea, Libya and Iran, and Biden is just plain absent/weak which encourages war. Geopolitics are just not a strength in the Democrat party.)