I don’t believe, were I an American archaeologist, whether working in American prehistory, or prehistory of any ancient culture, or working in historic archaeology for that matter, that receiving that image is going to scare me in the least.
Does anyone honestly believe a typical reaction is going to be “Uh, oh. This could be a big problem. This looks like it might upset the consensus interpretation of prehistory in the Americas”. If one thinks that would be the first reaction, I can only say I doubt it. Nobody is sitting there in their campus office saying “hope I don’t get any archaeological anomalies today. They scare the daylights out of me.”
I can think like a professional. It ain’t that hard. They happen to be human like myself, and I’ve seem a lot of artifacts, from a lot of cultures. My first reaction, with that in mind, might be along the lines of “I have no idea what I’m looking at”, or “what the heck is that?” I might think “well, that’s a mish mash”. Really, the last thing I’m gonna think is “uh, oh, this is dangerous to my world view”.
Since I’m usually courteous when someone sends me photos of things, I might at least write back “Sorry, but I’ve never seen anything like that, and I have no idea what it is or who made it, or when it was made”.