No Northwest Ordinance of 1787. Rather than having existing states abandon all claims they had on western territories and create a mechanism for the routine organization of new states out of newly acquired federal land in "the Northwest" (todays Midwest), no 1787 NW Ordinance means the existing states in the early 1800's hold on to their western land claims, restulting in many of the original states spreading westward in a series of long, narrow, and at times discontinuous horizontal bands, adjusted as necessary to resolve conflicts. As this becomes increasingly tricky after the Louisiana Purchase and (if this occured in this TL) the annexation of Texas and Mexican territory north of the Rio Grande, some new states come into the union that reflect the different history and background of these states, but a precedent has been set for reallybig states - at least as big as Texas.
In this scenario, I'd imagine around 20 states in the contiguous US:
The original 1787 states, at least 3/4 of them extending to the Mississippi River in one way or the other plus the following complete speculations:
Florida (possibly including the panhandle extending to the Mississippi River)
Louisiana (OTL's Louisiana including all or parts of OTL Arkansas, Missouri, and Oklahoma)
Dakota (Both OTL's Dakotas plus Nebraska, Kansas, Iowa, Minnesota and parts of eastern Colorado, eastern Wyoming, eastern Montana)
Montana The Rocky Mountain area north of New Mexico/Arizona (basically Western Colorado, Wyoming and Montana and Idaho)
Hispania Areas ceded by Mexico with a substantial preexisting Spanish-speaking population (parts of west Texas, New Mexico, Arizona, parts of California)
Deseret You got it! What US alternate history is complete without this! The Mormons in Utah and extending into adjacent parts of Nevada, Idaho, western Colorado, etc
Columbia The Pacfic Northwest, but bigger (Oregon, Washington, northern California
Texas OTLs Republic of Texas with the Nueces border.
There might also be some sort of "Indian Reserve" somewhere that is federally administered (maybe OK and KS) or father west
In such a time line (in which the federal government had no consistent role in how the new states were established and organized as it does in OTL) I'd imagine more differences in local culture and law among the states. The whole US might be a looser confederation of states. Of course the more likely outcome of (no northwest ordinance) is eventual war and conflict among existing states for the west, no US constitution and no federal union, and the eventual balkanization of the US with most of it being reabsorbed by British North America. Not a bad outcome for this Anglophile Yank, actually!