The difference between Japan holding the Majority and China holding it is that Japan doesn't have a policy of expanding it's territory, which China does.
Actually, I don't like us owing too much money to anyone, even if it was Canada or Great Britain.
I agree that we have way too much debt regardless of who buys it. My grand kids will have to pay it back to whoever owns it, and no country can thrive under such a burden. Actually survive might be a better word than thrive. As for China, there is a view that says the more their economy depends on our economy the better. They will then be less likely to act against our interests if such action could impair our ability to repay them or cause a drastic decline in the value of the dollar. Either way, I hate debt and deficits.
About 50% of the $7.5 trillion publicly held debt is by foreigners.