America
did have leverage to negotiate a serious and unprecedented peace, too. They have the weapons to power-gap Russian equipment, a Navy that could crush Russia's fleet in an hour of surface combat, and enough soldiers to deter even a multi-coalition Russian attack. There are a multitude of ways for America to offer support without putting America at risk.
Abandoning control in the European theater while doubling down on the Levant is like if the USSR announced they forfeit the Cold War to focus on Afghanistan. It is a bloody warpath, dictated by nonsense. Trading one proxy war for another isn't going to save the American economy, or improve American security.