Let's see, Australia owes over 7 trillion dollars of debt. The US which has a population of over 300 million owes 21 trillion but of course, central banks will come to save the day by printing more money out of thin air, right? . We are so screwed.
http://www.australiandebtclock.com.au
Hmmm . . . this website http://www.usdebtclock.org/ says the total US debt is 71 Trillion with GDP 21 Trillion - so total debt is about 3.38 times gdp. Aus 7 Trillion with GDP of 1.7 Trillion so debt is about 4.11 times gdp.
Just looking at debt figure on its own doesn't show the whole picture. It needs to be taken into context by comparing to percent of income and interest rates. Interest rates have come off a lot in the last 30 years - and maybe that is the whole conspiracy theory of why interest rates are so low and will likely continue to be low - due to so much world debt.