Im not 100% clear why we wouldnt want to get involved here, if ever there were a time to get involved.
Ukraine disarmed itself in 2006 at our urging, with the understanding that we would come to their aid if ever it were needed. At the same time, having a superpower like Russia going into full imperialism mode is good for noone but Russia. A tepid response like the one theyve been given will only encourage further aggression.
Assuming that you are implying American boots/bombs on the ground in the Ukraine, are you crazy? I mean seriously. Are you? There is in my opinion a dangerous detachment from reality in some circles of American political discussion about confronting Russia. Perhaps you may feel my language is inflamatory. But I get kind of disturbed when so many people, including those in power, put forward actions which would likely lead to thermonuclear war.
Looking back at history, there has never been a shooting war between the Soviet Union and the US. Never. The Cold War? It was always fought between proxies of the great powers. We would sell arms to pro-US or anti-Soviet interests (like in 1980's Afghanistan), or we would directly confront pro-Soviet interests (like in Vietnam). We came close to a shooting war with the Soviets more than once (the Bay of Pigs in Cuba). But such a war never happened, because those in power knew that such a war would inevitably decay into a thermonuclear war that would likely end western civilization with the press of a button.
The proper response to this is to strengthen military forces in new NATO member states surrounding Russia, including US boots on the ground. This will make a clear line that Russia knows it cannot cross without provoking all-out war. Unfortunately Ukraine is not part of NATO. We might be able to sell arms to Ukraine, but there are risks and limitations to this. What must be made clear to Russia is that if it enters Ukraine, it will face profound economic isolation. If it goes further it must be clear that it will result in WWIII. Thus we end in a stalemate. Not unlike the Cold War.