If you try to nip potential world wars in the bud, you face the situation above but end up with far fewer casualties.
From my point of view, nipping a world war in the bud is as easy to do as time traveling and stopping the assassination of Lincoln.
Protect your own country from direct threats, project force on a limited and intense level, and let the world war develop and envelope the entire rest of the globe if necessary. The important part is be prepared within your own country, because all you end up doing by trying to stop something you see happening is, bankrupting yourself, and causing unforeseen consequences. Once you are broke and now have more conflicts in more places to fight against, the public has no will to fight. In the end, you lose as surely as the British empire is no more. Peace on this Earth is something that MUST be imposed. Americans do not have the heart, the spine or the will to impose cigarette smoke on someone, let alone peace.
We can’t wall ourselves off from the world without serious effects.
And modern world wars would engulf us even if we tried to opt out.
You let the enemy feed on the weak, and he is only stronger when he comes for you.
Isolationism is merely wishful thinking.