A study by the Williams Institute at UCLA (University of California at Los Angeles) was published in 2016 I believe. It was the largest and most thorough determination of the trans population in the US to date. They put the trans population in the US at .6% of the population. There were 4 states, and California was one, that were are about .8% and obviously others were much lower. The complete study should still be viewable on their web site.
If you use 327,000,000 people total for the US population, that is about 2,000,000 trans people in the US.
Here in California the total population is about 40,000,000 which is about 320,000 trans people.
I live in Southern California in the Coachella Valley. It is made up on 9 contiguous towns: Palm Springs, Rancho Mirage, etc. with a total population of about 350,000 people. The trans population is about 2,800.