What if the Spanish had not only introduced sheep, donkeys, and horses to the North American West, but camels as well? Basically, camels becoming to the Southwest (and Mexican North) what horses were to the Plains.
What I'm imagining is that Spain saw the often dry North of Mexico before them, had some bad experiences fighting/supplying fights against the locals in the area, and one Spaniard decides to bring in some camels there (because it's dry), perhaps comparing it to Morocco. Before long, Spain has a decent amount of camels in North America, running the El Camino Real from Mexico City to the North. Camels will be brought into New Mexico as well once the Spanish get there.
Now what? Will camels be used for increased Spanish exploration and colonisation into the American West? Will an easier route between Mexico and California lead to earlier Spanish colonisation there as well? More Spanish in the American West in general, and as a result, more Spanish in the North of Mexico?
Then we consider the impact on the American Indians. First, let's say the Pueblo Revolt or some other event like it isn't butterflied, and from there we start seeing not only American Indian use of horses increase, but also American Indians using camels. Camels will be very suitable for peoples of the West to adapt, much like the horse was to the Great Plains.
Now, we know that the American Indians could be very adaptive of European introductions when they had the chance. Most famously, the Plains Indian use of horses. And also, the Navajo and their sheep, which were both purchased and raided from Puebloan and Spanish settlements. The Navajo created a unique breed of sheep, and readily adopted their textile industry to wool.
I bring up the Navajo because I envision the Navajo being a prime adopter of the camel, given their desert landscape and the potential use. Other groups I envision using camels is basically any group who in the 16th century lived in nowadays Sonora, Chihuahua, Arizona, Utah, New Mexico, and Nevada, and other parts of the Mexican North and American West.
What would they do with camels? I wonder if they would be able to adopt a pastoralist lifestyle using camels? The North American West does not have an animal like the bison to readily kill in large numbers. Assuming they don't go about the most obvious way and hunt the camels they get to extinction, perhaps a sort of Bedouin lifestyle could emerge? The camel becomes the central part of existence for these groups of people. Maybe even a mutation to allow for lactose tolerance in the groups most using the camel?
Camels and horses do not get along--the camel generally has the advantage over the horse in a battle because of this. And considering the dry lands of the High Plains (Great Plains were the Great American Desert, after all), I wonder if you could spread camels eastwards as well. Perhaps the Comanche to the north adopt horses, and the Apache do as well (as in OTL), but Comanche success causes the Apache to shift to camels, preserving a sort of balance in the Plains for the Spanish to mess around with. You can certainly hunt bison from camelback, although not as efficiently as from horseback.
The biggest issue for the American Indians is a Spanish, and much later (butteflies granted) American counterattack. While the Spaniards might be inept in the far north of New Spain (they had horses, it didn't help them much fighting horse-mounted peoples), the use of camels might help their empire thrive in those parts, along with other things like a balance between Comanche and Apache which a smart Spanish leader can use to play off both sides and minimise the damage to the civilian population of New Mexico and later Tejas.
For anyone not entirely convinced, the US Camel Corps recorded many successes in their short time of operation centuries later. Not to mention Australia's large feral camel population, which the American West would develop as well (comparable to the wild horse population).
Speaking of the United States Camel Corps, if the US still expands West, I'd assume much greater use of camels and possibly slightly faster settlement of the West. The Camel Corps would become a greater part of the military as a result TTL, and see action whenever the US is fighting in a desert (Mexico? North Africa? Who knows)
Those are some initial thoughts of mine, I'd love to hear other opinions about this.