I would describe that as suppressing ideas, not defeating them. Did we defeat communism in Korea or Vietnam? No, because the idea continues even after you kill off a sizeable number of adherents.
Perhaps the public was isolationist, but the US itself wasn’t. We were selling arms to whoever could pay for them and take them on their own ships (in other words, to the allies, as Germany and Italy had neither the hard cash nor the ships to transport the arms). And we pushed further in 1941 with the Lend-Lease act.
In the Pacific, we imposed economic sanctions against Japan after their invasions of various neighbors, including mainland China. China was included in the Lend-Lease act.
We may have been isolationist in 1930, but by the time 1941 rolled around, we weren’t any longer. That is what led to the attack on Pearl Harbor. It’s worth noting that we only declared war on Japan for their attack. It was Germany and Italy that declared war on the US because of the treaty they had with Japan, drawing us into the European portion of the war as well.
I’d argue that Vietnam and Korea had a rather explicit goal - stop the expansion of Communism in the far east. Afghanistan was similar - stop the return of the Taliban to that country. Unfortunately for all three countries, there were significant numbers of their citizens who wanted those ideas (Communism and Taliban) to rule in their countries. Like I said earlier, that’s trying to defeat an idea - and that’s an impossible task. The stated goal (stopping the spread of ideas) is an impossible one.
On the other hand, WWII and Iraq 1.0 had clearer and obtainable goals. Evict German forces from France and Poland and Russia and a couple of other places. Evict Italian forces from North Africa. Evict Iraq from Kuwait. Those goals are easy to measure. And once they are accomplished, you’re done.
That’s why I put Ukraine in the latter group of wars. The goal is to assist Ukraine in evicting Russian forces from Ukraine. Certainly that will include the Eastern provinces of Ukraine. Crimea may or may not be included in that goal. Frankly, it probably should be, as the whole purpose of Russia invading Ukraine is to get a land based route from Russia into Crimea. It’s a pain to manage Crimea via ship and the single bridge across the Kerch Strait to mainland Russia. Much better (for Russia, anyway) to have a second route through Eastern Ukraine. At any rate, the goal is easily measurable and it is attainable.
The only impediment to attaining that goal in Ukraine is the willingness of the formal and informal allies of Ukraine to provide some portion of the war materiel needed to accomplish that goal. I’m pretty sure that giving Russia a good kick in the pants is something that a decent portion of the US population will support as long as progress is made - and the number of body bags headed to the US is tiny.
–Peter