I don't think our response has to be public. In the past it often wasn't. If my history/understanding is right, the Berlin airlift was very close to, if not sometimes, actual air combat...which I don't think was public knowledge at the time. In addition, again based on limited knowledge, we sent nuclear armed B-29's and P-80's to England during the event as a threat. At that time, I think it would've been one sided in terms of nuclear exchange, and therefore a pretty clear message as to our potential next steps.
Fast forward to Korea, both sides pushed the envelope a bit, secretly. US jets flying into China, and Russian pilots flying against US pilots over Korea as "advisors". Cuban crisis? Really close to the edge, and months after Russia pulled missiles out of Cuba, we pulled intermediate ballistic missiles out of Europe. I think not to return until the Reagan era.
My point being not only are we not as close now as we were in the past, but that we've gone down this road before, and the response doesn't have to be public to be effective.
As to leadership, part of the above happened during the time of Stalin, who was far more dangerous than this guy. Much smarter, much more ruthless, and probably crazier. He was absolutely paranoid, but I'm not sure if he was a coward. I don't know if anyone alive really knows, but my belief is that his own subordinates eliminated him, as they recognized he wasn't good for the country anymore, and was too reckless. That type of regime change is always a risk in that country, probably has been since the beginning of time.
I think our overall goals here are twofold - to help Ukraine liberate itself, and to help Russia lose as many assets and dollars along the way as possible. I think both goals are admirable.