Liberals want things like less military spending, more peaceful approaches to international politics, no more proxy wars, and no more hawkish behavior (like us shooting down Iran's drones). There's so much war weariness from the Middle East that liberals have it in their mind that the US is the bad guys, that we are the militaristic aggressors, that we cause all the problems.
I don't really like hawkish behavior either. Of course I want free healthcare and to not have to worry about war. Obviously reducing our presence in the ME would be great. But the reality is that China is essentially re-inventing colonialism, rapidly making military advances towards Taiwan, gobbling up islands, viciously oppressing their citizens, inventing new and terrifying surveillance technology, slipping their malware in front of our children as apps and games, and just generally bullying other members of the world stage. The Russian government is killing political opponents, working on their own Great Firewall/retreating into their own Internet, systematically trying to weaken Western democracy with what is basically psyops, hacking the shit out of everyone they can, and building ASAT/hypersonic weapons specifically designed to attack American resources.
Basically, the enemies of the US seem like they're spending massive amounts of time and resources trying to destroy us on every front. Meanwhile America, still can't get electronic voting right four years later, and was close to defunding its critical defense infrastructure: https://www.defensenews.com/congress/2020/07/01/next-gen-icb...
America has a lot of problems but compared to this kind of behavior, we are definitely not the bad guys. Nearly all of the anti-patriotic sentiment I've seen ("America is third-world", "America is stupid and racist", "I'm moving to Canada because I hate the government", "Everyone else does it better", "I would never work for the government", etc) is coming from the Left. They should be more honest with themselves about both the good and bad things about America, because we need to fix race relations, healthcare, education, etc. but we definitely also need military spending. Cause fuck China.