They can't be called in early. They are specifically known as "Non-callable", which means that they
can not be cashed in at all before their maturity date. The only thing that can be done with them is that they can be sold to somebody else.
Period.
China owns more than $859.4 billion in U.S. debt. That's less than the U.S. debt owned by Japan but it only represents about 2.6% of the total U.S. debt.
www.investopedia.com
Now they can at the time the bond matures demand payment and not invest it in more Treasury Notes. No big deal, the Government just cashes them out, then sells a note to somebody else. That is literally what happens at maturity anyways. Except instead of giving them cash they give them a new note equal to the old one plus interest.
So to say it simply, that is a lie. And it does not matter, because if China cashes them out, there are other people waiting to buy the replacement bond. They are one of the most in demand bonds in the world because of their stability. The most they could do would be to decide to dump them. That would cause a small blip on the exchange market with that many coming available at one and reduce the price, but that is inconsequential as that only affects the amount they trade for, and has not a damned thing to do with the actual face value.
Only as Federal Income Tax, not even Capital Gains taxes. And they are not taxed at all at the state or local level.
And the taxes can be deferred, which is what most investors do. So long as the interest is reinvested, no taxes are collected on them at all until they are finally withdrawn and not reinvested. That is why they are the backbone of most 401k programs. Let the money grow, and so long as the money remains invested no taxes are due on it.
I think you will find damned few that invest in Treasury Notes who simply invest once, then pull the money out at maturity and walk away. The closest to that I can think of that do that are Savings Bonds. But those are also very specific. Their maximum face value is no more than $10,000, an individual can purchase no more than $10,000 of them in a year, and they are non-transferable (except for the death of the holder). Those can not be bought or sold, period.