For the next installment, check out Alternate History #5, Colonial Japan.
Among many reasons Mexican colonial history is fascinating, here are two: first, the Spanish settlement of the Americas began in earnest in the early 1500s, well over a century before the English did the same in the lands to the north. In a sense, these were medieval knights meeting Aztecs. Second, the initial Spanish explorers and colonists in Mexico found a harsher, more alien environment much closer to the coast, and much sooner. It wasn't until the mid-1800s that the now-independent English speakers to the north were trying to cross and tame the dry mountainous wastes in the interior; but try making the four hour drive from coastal Veracruz to Mexico City, and in the first hour you go from pleasant tropical coastal plains to rugged high desert. Those medieval knights were catapulted straight into the Wild West. English speaking civilization had some time to acclimatize on the somewhat Europe-like East Coast.
Alternative geography can be just as fun as alternative history. This is why the pope of alternative history Harry Turtledove has played interesting games with geography - in Down in the Bottomlands, he imagines the climate and politics of a world where not only did the Mediterranean never re-flood, but Neanderthal nations exist alongside those of Homo sapiens. In Opening Atlantis he imagines the East Coast of North America as if it had broken away from the rest of the continent, like North America's Japan or New Zealand; it would be closer to Europe and therefore discovered earlier.
A tylosaur skull found in the early twentieth century in Kansas. Tylosaurs were open-ocean predators.
At one time there was in fact a sea coast along what is now the western U.S. - the Western Interior Seaway during the creataceous. (This is different from what Turtledove imagined, which was essentially an East Coast broken off at the Appalachians and moved east.) The cretaceous seaway is why we find marine fossils in Kansas and Montana. Of course at that point there were no people to colonize North America yet. In fact there may not even have been any primates yet.
Imagine that not only the geography of that western continent stayed the same to the present day, but that there was no eastern continent at all. The experience of English speakers would have been more similar to the Spaniards, encountering high mountains and deserts and alien environments a day's ride from the coast. Agricultural land would have been more valuable; on the Western continent there couldn't have been the same real estate crash that happened shortly after the Revolution, during our expansion over the Appalachians, that drove Thomas Jefferson into relative poverty. The coasts that turned into ports and market places would have been more valuable as plantations, as remained the case in Virginia and the Carolinas (where the mountains were indeed higher) and of course in Veracruz. From north to south, Missoula, Idaho Falls, Salt Lake City, and Gallup would have been port cities with their backs immediately to the Rockies. (Note too that in the real world, this was almost all Spanish territory first.) They would have been greener and less continental in their climates, but the interior encountered by John Smith would have been a place of mountains and deserts unlike anything he'd seen in Europe. The settlers of Jamestown would've had to become King James's first cowboys.
What If Europeans Really Did Discover America?
There's another surprise in store for the pseudo-cretaceous John Smith: in this world, Europeans really are discovering the Americas. There was no land bridge; the Europeans are really the first ones there. Excellent! No need to steal anyone's land or oppress native cultures! Good news, right? Wrong.
About the time that the first Native Americans were colonizing the interior of North America, 10,000 years ago, there was a megafauna extinction. We're not yet certain that it was the paleolithic Native Americans who did it, but that's the best guess so far: humans are pretty good at disrupting ecosystems, through some combination of hunting to extinction, altering landscapes with fire, and maybe even bringing a few non-native organisms with them. My bet is that it was indeed the paleo-North Americans that did it. (Note to paleo-North Americans: Thanks. The Western U.S. is still scary enough with mountain lions.)
And that's lucky for the real John Smith, and non-Native Americans: not so lucky for when pseudo-cretaceous John Smith goes up into the mountains that begin twenty miles from the port of Gallup, because it's going to be a regular Land of the Lost up there. He's going to meet mammoths, and sabretooth tigers, and dire wolves. Sabretooths are bad enough, but dire wolves move in packs and weigh about 150 lbs. (If you're in Los Angeles check them out at the tar pits.) Sure there will be tortoises and sloths for him to eat when he's out in the bush, assuming he remains at the top of the food chain. I'm imagining a battle during the pseudo-cretaceous American Revolution, when the British regulars are charging the American lines, only to have the battle end in a panic when a herd of mammoths emerges from the Rocky Mountain forest, scared by the cannon, charging the field and scattering the soldiers of both sides. Or maybe Cortez's party turned back to the coast when a pack of dire wolves comes out of the brush near Texcala, not slowed by their primitive guns, and kills dozens of men in full armor and sends the rest running back to the coast wetting their pantaloons in terror, cursing their leader for burning their ship and trapping them in this hellish land.
Hey Lewis and Clark: how far do you seriously think you'll get in this place? By yourselves, with no native guides? The only other continent with comparable megafauna to this is Africa, and it's right next to Europe, and in the middle of the nineteenth century Europeans were still exploring the interior.
There have been alternative history/borderline fantasy books written imagining an America with dinosaurs still running around - in particular, Kurt Giambastiani's The Year the Cloud Fell, which features Custer's much more evenly matched war against the Cheyenne Alliance, interrupted by T. rex attacks (In this world's Dakotas, Sue is still alive and well.) The dinosaurs in the American West with Native Americans meme is over a century old so I'll send you here for more.
It's hard to say how different a pseudo-cretaceous North America would look and how it would effect the world. Assuming initial Spanish settlement, it's possible that Spain would have dominated the entire New World, without allowing any of the other powers to get a foothold. The land would have been more mountainous and drier on average and much less productive; and the dangerous wildlife would have dramatically slowed development of the interior. Without a native population to enslave, the riches that Spain extracted from the New World would have been much slower to come. This may have meant a faster decline of Spain, and a quicker rise and larger relative role in European history for the Netherlands, whose trade empire was only partly dependent on the Americas. The Netherlands may have ended up playing a role in the Age of Discovery in the rest of the world more similar to Britain. Home rule of the Americas would have been much slower in coming.