In Estonia we call it “rootsi laud” or “Swedish table”. You can just keep on going to refill your plate with anything you want. On average people pay for more than they eat so the few outliers like me stuffing tons of salmon on my plate don’t make the place bankrupt.

I think hotel breakfasts do this in most of the world, but here we also have it on ships, where the food is actually good

So no, it isn’t unique to the US.