Well, in war, anything goes.
Putin is targeting the prime minister of Ukraine, so, why not do the fair thing and target Putin?
In WW2, Hitler was a target, and in all wars, the leaders of the opposing sides are always targets. Putin is the prime target, and there should be nobody in the world opposing placing Putin as a target of war.
And this, ‘why don’t you go after him yourself’ is pure nonsense. There are always people more capable and better equipped and with easier access, that can do the job.
Is America in a war? So far I’ve seen Russia and Ukraine in a conflict. How does that translate to America is at war?