But why would they? They would have to purposely transport these animals about 3,000 miles north to get them to suitable climates, when there were better places to colonize near them. You could sail from Peru around the south tip of Chile to Uruguay for the same effort. Compared to this, leading a llama caravan through the Andeas to settle the Argentine pampas is a no brainer and yet they didn't do it.
This is about as plausible as Chinese colonization of North America. People are rational. They wont take the road of most resistance when they have better and nearer places to colonize if they were interested in that sort of thing.
Yeah, but we aren't talking about Andean colonization of America. No one has suggested that.