For many years, I lived in an oil state. One of the main features of oil states is government that is totally unaccountable. Since the people aren't taxed very heavily, they don't really pay attention to what the government does.

Holding the reserve currency may have had a similar effect on American politics. A lot of government expenditures are funded via inflation, rather than taxation. That means there's less popular resistance to waste, fraud, and abuse than there otherwise would be.