The amount of debt they hold is about $1.2 T, not trillions plural. They own less than 10% of our total debt. Being owed money is not an insulator again conflict or war. Germany owed massive amounts of money to Great Britain and France after WWI. That did not stop them from declaring war after the German invasion of Poland .
Germany's economy was not totally dependent on trade with them either.......
China's economy is totally dependent on trade with the U.S. at an estimated $45 billion in exports to the U.S. Starting a war would stop the exports and shut down their factories. Couple that with the billions of dollars of food stuffs such as pork, chicken, soy and corn they import from us just to feed their own people, a war with us would also result in the inevitable starvation of many of their people.
Nope, China isn't going to start a war with us......What's that old saying? "An Army marches on its stomach"....