Its not like the US hasn't done big ambitious things before: Social Security, Medicare, Medicaid. Hell didn't they help develop some of the social programs for Post WWII Europe/Japan etc?

Post Nixon the government really just got captured and paralyzed and so a generation has grown up not understanding that this is a deliberately broken government, not how a government can operate. Instead people have been raised to think that all government is just ineffective and naturally broken. The only people who actually get it are the subset of Americans who have traveled or lived overseas for some time. As of 2023 only about half of Americans have a passport so there is a large chunk that haven't seen anything else.