In times of war, this USD debt is going to be a liability for china, since the US can just refuse to repay it (and after all, what else is china going to do about? Declare war again?).
Kind of explains the problems with China having too much USD debt. Even without times of war.
This is a contradiction. It leaves open the possibility of sanctions sufficient to induce US companies to stop building everything in China.
In the long term the cost of this is negligible or produces a net benefit. Maybe some things cost more if it would have been cheaper to make them in China, but that isn't necessarily true outside of China's cross-subsidies which you're then still paying for, and even if they do you get the countervailing economic benefit of repatriating some of the production. (It's also plausible that sanctions on China would move production to places like Mexico and Brazil which are still cheaper than the US, but then you're back to no significant long-term cost increase and a benefit from diversifying production.)
The main cost is in the short term, because things would cost more. But they would cost more by the amount of the tariffs. Which go to the government, which it can then give back to the domestic population in various ways. Which could produce a domestic benefit, if China ends up paying any of the tariffs. If there is a $1 import tariff which pays for a $1 tax reduction for the middle class, but the tariff is paid $0.75 by the domestic buyer and $0.25 by the foreign manufacturer, you just transferred $0.25 to the domestic population.
The only way you even get a short-term domestic cost is if manufacturing actually does start moving out of China. Because then you have a $1 tariff which causes people to be willing to pay $0.25 more for a product made in Ohio or Mexico. Which costs you the $0.25 and then you don't get the $1 to offset domestic taxes. But it costs China $5, i.e. the full value of the sale and not just the amount of the tariff or the marginal cost of manufacturing it elsewhere. It costs them more than it costs the US. Which gives the US more negotiating leverage to get whatever concessions they want.
No one is expecting war this year. There will be 3 Ford Class carriers by 2030 and 5 by 2040. As well as the Nimitz class which are still better than what China has today.