It's always seemed strange how salary/pay is a "private" thing in American culture. In NZ, AU and UK it's something that could be brought up at a party (if talk

It's always seemed strange how salary/pay is a "private" thing in American culture. In NZ, AU and UK it's something that could be brought up at a party (if talking about work), and no one would think it was rude. Is this because people feel judged about how much they make in the US? (At least, more so than other countries?)