The US doesn't have old culture or folk traditions because we are a young country, full of people from other places. Our strongest traditions come from our holidays, yes, but more than just black Friday. We have the whole month of December that is the build up to Christmas and New Year's - with decorations and music and foods and general good will that's missing the rest of the year. We have other seasonal traditions as well. But, you're right. Our Christmas music is probably the closest thing we have to traditional folk type stuff, and it's mainly from the last century. So far as music genres, everything from motown to country & western to (heavy metal and) rock to bluegrass to rap was invented (or at least popularized) here. Not sure what else you are looking for on that front.
While I can appreciate the metal and the celebration of Maori culture for sure, that video would seem a little more legit if it weren't being played by a bunch of ginger looking dudes (instead of say, Polynesians). Not sure how they play into Maori culture.