If my knowledge about China's history is correct, there was no one "China" until the Qing dynasty, at least not in territory. The earlier eras were all pockets of land that's a part of modern China, but not China as a whole country. Of course, if you include the Yuan dynasty, which BTW was ruled by the mongols, then there were two whole"China" in history, sort of.
That's why I'm writing here. China as a whole had only existed in a rather recent history, at most a few hundred years, not thousands of years. The Modern USA on the other hand has not break up yet after their union, aside from the civil war. IMO, comparing the "Thousand of years" China and "Hundreds of years" USA are like comparing apples and oranges.
Also, this might be relevant since it's about China's territory. The current China's territorial claim is mostly based on the legacy of the Qing Dynasty, which includes modern China and Mongolia. Before Qing, Hong Kong had been a part of China, but get this; Taiwan hadn't! Hence if you want to be political and say Taiwan is Chinese territory because it had been so for thousands of years; sorry, it doesn't stand. But if the reason is because China's claim is based on Qing's legacy and Taiwan was under Qing's control, then okay. Just make sure to sort out the mess of modern world politics.
Okay. Back to the topic.