I’m sorry for not getting this, but when did they celebrate foreign wars?
Syria, four years of Russia!Russia!Russia! turning into the presently-unfolding Ukraine conflict, even to a lesser extent Afghanistan where a not-insignificant number of paid shills have advocated ongoing US military presence. (They call it "peacekeeping" or "human rights oversight" or some other euphemism.)
I think the other euphemism you're looking for is R2P. Once the Democrats (I can't call them the "left") latched onto that, they discovered -or rediscovered - an appetite for foreign wars. But it takes some real revisionism or selective memory to pretend that the Democrats are unique in getting into stupid foreign wars. in addition to Afghanistan, which you mentioned, let's not forget Grenada, Panama, and Iraq (twice). Enthusiasm for stupid and often unsuccessful invasions of foreign countries isn't a left disease or a right disease, it isn't a Democrat disease or a Republican disease, it's an American disease. All parties are complicit, either in starting them or in continuing them.
Look at Iraq 2, surely the most egregious example in recent memory. Who in congress was in favour of that needless adventure? Just about everybody, either gung-ho loudly chanting U-S-A! U-S-A! or reluctantly but afraid of looking weak. Who opposed? Well, a lot of Democrats, but their opposition was confined to the vote. For ongoing, sincere opposition: what passed for the "far left" (Maxine Waters and Dennis Kucinich) and the Libertarian right (Ron Paul). Kucinich and Paul, unlikely allies, really found common ground in that but they were voices in the wilderness. They didn't have a lot of friends, left or right.
Nowadays, it does seem that scepticism about foreign adventures in America is more of a "right" thing (the right trying to forget how loudly they cheered such madness in the past), but even if it's a rather belated conversion, it's still welcome as far as I'm concerned.
On the other hand, how sincere is that conversion? I suspect a huge appetite for foreign wars is still lurking just beneath the surface, even on the right. Just waiting to be rediscovered. Check this out, from just the other day:
https://www.msn.com/en-us/news/world/candace-owens-called-for-the-us-to-invade-canada-to-stop-justin-trudeau-cracking-down-on-trucker-protests/A call for R2P but from the right. Makes you wonder if anything has changed.