Yes they have huge national debt but in relation to GDP, which is that actually matters, it's not that big. Look at Italy, Greece, Spain, etc they also have a lot of debt, Greece went bankrupt and put the euro in danger. US has more economic growth on average, most important companies and low taxes/regulations. EU has shitty central bank with negative interest rates, quantitative easing and constant flow of money from North to South.
Please don't tell me EU economy is superior to that of the US