Well Pompous when people took out a mortgage with a 1% teaser rate in 2004 their interest payments were quite low to, but as we can see that can change pretty quickly.
Also that isn't the best indicator.
Look at debt service as a percentage of GDP. Look at debt service as a percentage of revenue. Look at public debt as a multiple of revenue.
You want to look at the expert on sovereign balance sheets its Professor Rogoff. He is a Keynesian, but he isn't dogmatic like Krugman and is just really good at gathering research so he has my respect.