It depends ..

China still have a lot of poor people.

Normally you want credit to flow from richer parts of the world to poorer parts of the world - where there is a lot more potential for growth.

NNIT is meaningless metric for larger countries.

China is a net creditor because they have certain national interest, their large credit position provides a buffer in international trade.

US acts a gold vault in international trading, China has certain industries that "generate gold" but their main focus is meeting the demand for their domestic market, just like most other countries in the list.

No but it is probably not a great idea to let it go unchecked either.

You're assuming we're maximizing the productivity on our debt. I would say the US is spending money on the government equivalent of takeout food and flatscreen TVs.

4K TVs are incredibly cheap yet good quality these days, and it's not like you need more than one.

That wasn't really my point, my point was that we take on enormous debt and we spend it on things that aren't the best. Why don't we spend more on infrastructure, research, investing in clean energy, etc? I understand that we need a military to protect our position in the world, but I'm not sure $750 billion dollars per year is needed. Sure some of that is spent on research, but I think there are more efficient ways to spend the money.

Well, because everyone in the US has brain damage from inhaling leaded gasoline in the 80s, and so they're stuck in 1992 and think all government policy means bombing countries in the Middle East while ignoring Asia, Africa and their own country.