Very curious. Wasn't it about 12,000 years ago that Asia orientals walked over what is now the Bering Strait to become North America's Eskimos and American Indians? Maybe this explains why China has these characters but the American Indians don't.
Last year, in a book entitled Origin of the Olmec Civilization, Professor Mike Xu, a Chinese who teaches in the foreign languages department at the University of Central Oklahoma, proposed a hypothesis which aroused a storm of controversy in archeological circles. In Xu's view, the first complex culture in Mesoamerica may have come into existence with the help of a group of Chinese who fled across the seas as refugees at the end of the Shang dynasty. The Olmec civilization arose around 1200 BC, which coincides with the time when King Wu of Zhou attacked and defeated King Zhou, the last Shang ruler, bringing his dynasty to a close.
Furthermore, Xu had "explosive" evidence in the form of the written word. Over the past three years he has found some 150 glyphs on photographs of and real specimens of Olmec pottery, jade artifacts and sculptures. As well as himself leafing through dictionaries of ancient Chinese, he has also taken his drawings of these markings to be examined by mainland Chinese experts in ancient writing, and most have agreed that they closely resemble the characters used in Chinese oracle bone writings and bronze inscriptions.
A big ol' batch of Asiatic type people moved to America circa 5000 years ago. They are the Na Dene ~ Navajo, Apache, Yaqui, Aztec (and others). Sioux sign language IS Shang Dynasty characters. I don't know if the Navajo still use them.