What do you think of claims of pre-Colombian contact between East Asian and Indigenous American peoples?

Not something I really know a whole lot about.  It doesn’t strike me as wildly implausible – we know there was probably occasional contact at some point between Polynesian and South American peoples, because (among other things) New Zealand and other Polynesian islands had potatoes before European colonisation, and the Pacific Ocean is not naturally a tenable habitat for a potato.  I’m not aware of any hard evidence for, say, Imperial Chinese missions to the Americas pre-15th century, though.