As far as Texas goes, the richest and most readable source I've found is Fehrenbach's Lone Star: A History Of Texas And The Texans. It begins with what we know about native life, how the Spaniards came to regard the land as their own, and how Moses Austin came to bring the first large group of Anglo settlers into the area we now call Texas in the early 1820s — then it proceeds through the tensions that led to Goliad, the Alamo, the independence of the Republic (1836), and finally the introduction of Texas into the United States (1846). That should cover your timeframe quite well.

Basically, there were disparate groups of natives in Texas, mostly nomadic and most of whom we suspect were figuratively decimated by settler-borne illness. The land wasn't especially hospitable, so natives largely stayed on the move. Fehrenbach relays a strategy practiced by some natives where they would spend sometimes half a day catching a fish, then split it open and leave it out on a hot, flat rock, away from ants. They then stick to the shade for the next day or two — I forget exactly how long — until enough maggots have grown in the fish meat that their meal would then end up feeling larger than it would have been otherwise. (I can't say whether or not the math works out on that one; if you're ever lost in the wilderness, please do not blame me if this method fails to provide more calories than simply eating the fish.) All this to say that the land was not rich in the kind of resources that would enable the more stable native communities seen in Ohio and elsewhere. It was a hard place to live, even with 19th-Century technology. The years from 1820-1845 were some of the most tumultuous and would be the most interesting to modern Americans, but I don't believe we have much to say about what was going on in 1776 where Dallas exists today.

Someone else will have to speak to the other areas about which you asked.

Well at the time they were a part of the viceroyalty of New Spain. The region was largely inhabited by natives, although the region was very sparsely populated to begin with. Presidios (spanish forts) and missions existed, but they were relatively few and far between. Alta California was not overly populated, nor was Arizona. In fact the Presidio that would become San Diego was founded in 1769, and Tucson would be founded in 1775. Although New Mexico had older Presidios and Missions such as Albuquerque (1706) and Santa Fe (1598) having first been conquered in the late 16th and early 17th centuries. Still however, it was a backwater even in the Viceroyalty. There were very few people, native or otherwise living there. It was as remote, very remote. The Russians meanwhile were settling Alaska, and the northwest was still being explored. In 1776 simply put there wasn't many europeans really there, and those there had nothing to do with the revolution. The west would be conquered largely after the civil war, when many former slaves and soldiers would move west seeking a better life (note: not everyone fell into those groups who were moving west).Additionally, it would serve as an outlet for new immigrants from Europe after the civil war as well. Other than California and Oregon, the west would become settled post civil war. This was in large part because of the Homestead act of 1862, which I'm not going to go into. The west would largely be shaped in the second half of the 19th Century. TL;DR Almost nobody lived there

I think you may be mistaken. There certainly have been histories written about the west before it was part of the US. You may have trouble finding them under US history because they were not US territories at the time. Look under California History or Texas History.

Lexington/Concord was 1775.