I think the biggest recent example is the Russian war in Ukraine. Usually it is liberal-types arguing against American forays into the business of other countries, but they are the same group demanding more money and weapons be sent to Ukraine.

Yes and no; the warmongers put a lot of money into persuading people who neither know nor care much about what is happening to support policies they don't take much of an interest in. We saw something similar in the 2000s where the right-wing types were very supportive of wars that in hindsight made them really angry at the Republican leadership for lying/facilitating them into several disastrous conflicts. I expect we'll see something for the left in a few years assuming we don't see a full WWIII escalation (or maybe even if we do). At some point the lack of any possible upside from or reason for US involvement in eastern Europe will be decisive.

The pro-war types don't have the numbers - US elections follow a consistent though imperfect principle that whoever is advocating for peace wins the election. They rely mainly on short term plays leveraging hysteria.