Based on your financial expertise, provide your response or viewpoint on the given financial question or topic. The response format is open.

Where do countries / national governments borrow money from? 
Typically the debt is held by individuals, corporations and investment funds, not by other countries. In cases where substantial amounts are held by other countries, those countries are typically not in debt themselves (e.g. China has huge holdings of US Treasuries). If the debts were all cancelled, then the holders of the debt (as listed above) would lose out badly and the knock-on effects on the economy would be substantial. Also, governments that default tend to find it harder to borrow money again in the future.