Pride goeth before a fall

If anyone had suggested America help bring about regime change in Moscow in the 1950s, 1960s, 1970s or 1980s they would have been mad. Nor when Russia invaded Hungary or Czechoslovakia did the Americans think of doing anything. 

When the Russians invaded Afghanistan the Anglo-Americans used the mujahedin to fight the Communists, something which was absolutely the right thing to do but which did convince Osama bin Laden that he had defeated the Russian infidels and could therefore defeat the Anglo-American ones. 

If Putin does go with American help, the Americans may regret it as they regret sponsoring Osama bin Laden. But that is how history goes. 

There have been many definitions of history but the best is one damn thing after another. 

Most wars achieve things the opposite of what those who start them want. That is true for Chamberlain and Daladier declaring war on Germany and Germany invading Poland, for example. 

Both Putin and much more so the USA are being very hubristic. "Pride goes before destruction, a haughty spirit before a fall" (Proverbs 16:18).