Hello. Ancient China was very different from modern-day China. They invented many things which led to many technologies that are available today. This link is for a school project, but it lists top 20 Chinese inventions.
It is refreshing to appreciate other countories' cultures without having political opinions on them.
They have no evidence that anyone came back and said guess what we found, there is a document from the first dynasty in china called "The Mountains of the South" that describes the mountain ranges from North America down to South America as viewed from the Pacific ocean.