What Chrissi said, exactly.
Black Friday, Black Week, Hallofuckingween, Valentines. It's all directly imported from USA entirely for commercial reasons, and don't corresopond with any Swedish traditions whatsoever. But they have been pushed heavily for 10-15 years, and so are now part of the mainstream commercial life.
Except that the rest of the world isn't populated by sheep who have no choice but to obey the wishes of the retail industry. Why not just ignore them?
I would especially ignore Black Friday, because as I said, I assume that's a normal workday for everybody. Why would people flock to the stores on some arbitrary day instead of going to work?
I understand how American movies and McDonald's and so on tend to dominate, because other countries don't churn out movies in such high numbers and there probably isn't as much money to make gigantic blockbusters which usually aren't that good but are at least visually stimulating. And maybe some people like fast food burgers and fries, so there's that.
But if Valentine's Day and Halloween sound stupid, the solution is pretty easy -- don't participate! (Except, as Chrissi said, it's pretty hard to resist giving cute little kids candy. But Halloween here is far more over-the-top than that.)
A few years ago, American stores started opening their Black Friday sales on Thursday, Thanksgiving, a traditional family holiday celebrated by almost everyone (because it's not religion-specific). But a lot of people, myself included, were opposed. They thought it was bad for the employees to have to work on a family holiday (apparently some employees like it but I'm sure not all do). And some, myself included, even thought it was bad for shoppers, who again aren't forced to go out but maybe want to get there as soon as they can to score the best deals.
But then a few stores, seeing the public opposition, started proudly advertising that they WON'T be open on Thanksgiving day. I think they got enough support that more and more stores are joining them.
So the influence can go in both directions!