Public schools get a lot of days off, but otherwise most of them don't excuse people from work (depending on employer of course). Retail gets shit for holidays, and generally get "floating holidays", basically come in on some holiday you should get off, then get some other day you want off. That national dog day or whatever you mentioned I've never heard of, probably just some stupid propaganda-style thing. We also have a black history month, course no one gets THAT off. I can't really speak for other countries (in case you can't tell, I'm American), but I don't think they really have any less holidays than we do. Germany gets 6-weeks paid vacation a year to my understanding. We don't get anything like that, and I don't think we have 6-weeks worth of holidays.
Also, you did completely misunderstand Thanksgiving, yes the original reasons were just that the settlers were really hungry and convinced the Indians to bring them food, but that's not what it's really remembered for. The First Thanksgiving was generally the turning point, when he learned how to not die in America, and we were able to hold our own here. So we give thanks for that and anything else in our lives. It's the whole, "appreciate what you got" thing, so that when Christmas comes around later we can switch to "beg for what you don't got".