The American security guarantee brings with it moral hazard, such that the countries whose security is tacitly guaranteed (Germany, et al) slack off and make their defense policy one where they fight any would-be conqueror to the last dead GI. The fall of Ukraine may be necessary to prod both Asian and European countries into spending more money for defense, just in case Uncle Sam decides to sit out an attack on these countries by a foreign invader.
That’s going to lead to war, not peace.