Debt is denominated in our currency- that makes a HUGE difference
Because all the debt is denominated in our currency, we can reduce the debt with both inflation and economic growth. The later is of course preferable.
America has been a safe haven for foreign investment for many decades and will continue to be. This is a good thing. More capital for investment in America vs other places in the world. Think about it this way, how would you feel if America was investing China at this level, and funneling all that capital out of America?