If you look at the total burden of debt in any given country you need to look at the borrowings of the state, of private individuals and of private sector companies. Inspection of total debt figures reveals that Euroland is considerably more indebted as a proportion of its income than the USA.(450% versus 300%). Japan is more indebted than either (600%). Ireland leads the list of highly indebted countries. (1000% GDP). Smaller countries with large banking sectors like Switzerland also tend to have apparently high leverage, as the bank balance sheets have a big impact on the national figures. The UK is more in line with Euroland, but has a better growth rate and a larger financial sector to assist paying and to explain the figures.
Household debt in the UK is below the levels (relative to size) of Denmark, the Netherlands, Switzerland, Ireland and Portugal, but higher than other European countries. Overall private sector debt in 2011 according to OECD figures in the UK was similar to that in the US at around 200% of GDP, well below the levels of the Netherlands, Japan, Portugal, Belgium, Ireland and Spain.
Japan emerges as a highly borrowed country in both its public and private sectors. However, it has very little external debt which is always more problematic to service and repay than local debt. It also now owns a great deal of its own state debt following endless QE programmes, which makes it even easier to service, and enjoys very low interest rates. It means its high indebtedness has not been a problem and seems unlikely to become one anytime soon.
The high debt levels in some Euro countries is more of an issue. Under the rules of the Euro so far they cannot print money to buy back their own state debts. Tougher ECB control of their commercial banks also means they have to rein in private borrowing through the banking system. It is interesting that neither of these rules has resulted in a more lightly borrowed Euro area than the USA, for example. It shows how a lack of growth makes stabilising and reducing debt so much more difficult.