I recently learnt that Denmark and the US are the only two countries with a fixed debt limit. Several other countries have relative to GDP debt limits. The purpose is the same; to ensure that executive branch can borrow money without having to ask the legislative branch each time. The US debt limit has existed since 1939 in its current form, but it was only recently (like since the 1980s) that it has become a hot potato. Denmark's has existed since 1993, and only been raised once, though far higher than the actual debt.
Other countries don't have these restrictions (fixed or relative), where it's usually because those countries' constitutions allow the executive branch to simply borrow money whenever it sees fit.
Other countries don't have these restrictions (fixed or relative), where it's usually because those countries' constitutions allow the executive branch to simply borrow money whenever it sees fit.