Most Amerikkkans don't actually get public holidays off in the first place.

Most do not. I only did once I moved into a white collar job, but not all white collar jobs do even.

Generally it's up to your employer. It can vary from state to state, but in California—one of the most allegedly "progressive" states in the country—it used to be that literally the only real legal protection was the federal one: that if you work more than 40 hours in a week and are an hourly or "non-exempt" worker, you have to be paid overtime. Recently it has instituted a couple more, such as requiring that full-time workers (with exceptions, of course; liberals LOVE their exceptions!) get at least two weeks per year of sick time separate from their PTO, and that if you have accrued PTO, it must carry over from year-to-year instead of getting lost, and must be paid to you if unused when you leave the company for any reason. I believe this bit about accrued PTO is why a lot of companies are moving to so-called "flexible PTO" schemes where the PTO doesn't accrue and is essentially limitless on paper (but of course, still needs to be approved by your boss, so it's essentially a step BACKWARDS where the boss has complete say and you get no protections at all, while being marketed as great for workers).

But no, there are still no legal protections at all for public holidays, unless you are an employee of the government itself, or certain semi-governmental agencies like public schools. If you work for a private corporation, it's 100% up to them whether to give you holidays, or pay you extra if you work on them and are hourly/non-exempt. It's essentially part of your "benefits package", so make sure you find out about it when considering whether or not to accept a job.