If Europe and Asia had fallen, we'd have been at the mercy of the Axis, it would only have been a matter of time. It's hard to think of tens of millions of deaths as being "an ounce of prevention", but I think the "pound of cure" had the Axis solidified their holdings would have been beyond insane.
I said Kosovo as questionable because this is also an ounce of prevention situation...by stomping on that spark, we likely prevented a wildfire that could have disrupted Europe, which we are too closely linked to for it not to affect us negatively. Also, it would be difficult to underfund against/underestimate the Serbian military, so it's not really "well managed" as much as "not applicable for failure".
Fair enough, but Bush and Co. used the same rhetoric in the run-up to invading Iraq. "Prevention," "destabilizing the area," "he already gassed his own people," et al. I am a noninterventionist at heart.