Just ignore Portland, Seattle and the entirety of NorCal, along with Denver/Boulder, and a bunch of other large cities in what some call the "flyover" parts of the US.

Excepting the coast, the western half of the USA is desert and mountains. There are scattered cities (Denver, Salt Lake City, Phoenix/Tuscon, Las Vegas, Boise, El Paso, Spokane), but most of the territory is relatively undeveloped and sparsely populated. (This is a good thing in my opinion. Covering every bit of land with city is a miserable societal goal. So is strip mining all of the land for fossil fuels and minerals, or turning it all to pasture.)

Here’s a map: https://johnstonarchitects.files.wordpress.com/2012/04/pop_l...

Even saying something like "California has a lot of people" can mislead you if you look at a map of the state. I live in Michigan and fly into Silicon Valley about twice a year; when I depart Michigan the entire state I fly over shows signs of human population, as everything is at least a farm [1]. In Silicon Valley, most of those mountains you can see on the horizon have nothing (visible from a plane) on the other side of them. Even most of California is empty mountain.

[1]: I have to qualify it with "the parts I fly over" because obviously I'm flying over the southern part of the state. Head north and you start getting vast tracks of wilderness, and the upper peninsula is effectively not populated. There's just a few beads of "civilization" tied together by some fairly long roads, which are themselves most of the rest of the "civilization", and then it's square mile after square mile of wilderness.

The western US is incredibly sparsely populated compared to the east. Just look at one of those nighttime satellite shots: http://geology.com/articles/night-satellite/satellite-photo-...

Also the 27 million people living in Texas.

Texas is 695,662 km^2. That's larger than the combined area of Germany, Belgium, the Netherlands, Denmark, and Great Britain (682,034 km^2), which have a combined population of more than 174 million people.

So, yes, Texas is comparatively under-developed.

Even regarding Texas, about 16 million of those 27 million live in just 4 metro areas (Dallas, Houston, Austin, San Antonio). Most of the the development, large metros included, is in the eastern half which is a fair bit less arid. Texas has 8 counties that make the top 50 least populous counties by density (https://en.wikipedia.org/wiki/County_statistics_of_the_Unite...).

It fits a pattern that also fits Australia and Canada... people don't want to live as much where it is extremely dry, or extremely hot / cold.