I also had the felling that it was somewhat a US tradition.

Open offices a much rarer in e.g. Germany. Through then Germany also has more strict labor protection laws wrt. office "safety/healthiness" so it might just not be as profitable to do an open office? (Note that I'm mainly referring to regulations about chairs, desks, light and noise in offices. Which exists but are in practice hardly if at all enforced on small companies. But from time to time in larger ones.)