Does the US pay its bills? Does anyone else?

Technically this is a GQ, but I thought I’d be safe and put it in GD:

A foreign friend of mine recently complained that the US doesn’t pay off its debts to foreign countries. I’m well aware that the US is typically behind on UN dues, but I have two questions:

1.) Does the US actually borrow money from foreign countries and not pay them back?

2.) If so, is this considered unusual? I had a vague memory of hearing that in general, countries typically all borrow money from each other and it’s understood that they’re going to be slipshod about paying it back.