Funny you ask about this, just yesterday I was conversing with an aunt of mine about the Incas and what uses they had for llamas.
I brought up a major issue with llamans being spread elsewhere in the New World, even just elsewhere in South America and Central America: From a climate and environmental standpoint, they're rather stuck. They don't do well in tropical climates. All right, let's say we don't want to spread them in the direction of the Amazon basin, or the Orinoco basin. Fair enough. But let's say you want to spread them in a northward direction, to Central America, and then potentially to North America.
I don't know if it's a similar situation to that of European chamois - an ice age relict surviving in the alpine mountain ranges of Europe and not really able to live elsewhere - but it seems it is somewhat similar.
Llamas and
vicuñas feel at home in a temperate environment, or a temperate environment that transitions into a colder mountainous or mountain plateau environment. They're not really well-specialised for dense Central American rainforests and for grazing there. They might be vulnerable to the heat and parasites.
Another issue is that between Columbia and Panama and Costa Rica, there are plenty of mountain ranges and dense tropical forests, often with no usable roads in the region. In an environment with a New World ancient-to-medieval society, spreading llamas northward by land would be a huge hassle. You'd be better off loading them on one of the large coastal rafts used by some South American native cultures on the Pacific coast, then somehow sailing over to central America, to at least the Panama isthmus. That still doesn't get rid of the problem of a tropical climate inhospitable to the well-being of llamas. Furthermore, are we sure llamas would even be willing to be ketp in a pen aboard these big sea-going rafts ?
If the Mesoamericans don't show an interest in using domesticated llamas and vicunas, particularly because of llamas dealing badly with a tropical central American climate, I find it unlikely llamas could spread from South America.
Back in the 2000s, Dale R. Cozort, a long-time and old-time affiliate of AH.com, wrote an interesting and detailed essay called
Llamas in the Appalachians. I don't know the details, but I think this has more of an evolutionary POD (so not a strictly realistic pre-1900 POD), with some branched-off species of llama relative surviving in nothern Mexico and then getting spread by natives around northern Central America and Northern America. But you'll have to read the whole essay for details.
I have zero doubts that llamas could prove very useful to Native Americans throughout the New World, if they could be spread easily. However, there are some genuinely big natural as well as logistical problems with that. I get the impression that if it was that easy in OTL, some native peoples would have eventually done it, sooner or later. Maize famously spread throughout much of the New World already many millennia ago, in a gradual and long-lasting fashion, even though it was initially a far more confined plant. Llamas are far bigger and trickier living beings to manage and thus harder to spread far and wide than a cereal crop. Even maize took many millennia to spread throughout the New World. The sheer effort needed to spread llamas widely, and largelly to only those environments that make sense for them as creatures, would be overwhelming. Especially with the simpler Neolithic-level technology of Native Americans in mind.