I can recall an article from American Heritage in the mid 1960s that discussed the possibility. There are a number of language and cultural cognates between Mayan and Chinese peoples. There is also the story in the 7th century Book of Liang by Yao Silian, about Hwui Shen, a Buddhist monk who traveled to Fusang (America?). This would place him in the Americas toward the end of the classical Mayan period, perhaps when Chinese concepts would be most influential. Interesting stuff.