It's the wild west in the US. If you have the money you can usually find a doctor who will do whatever you want. We can (and probably should) ask how often it's happening, but children are getting medical and even surgical treatment. I haven't seen any evidence of children under 6 getting hormones or puberty blockers though.
For example:
> Dr. Gallagher said she performed top surgeries on about 40 patients a month, and roughly one or two of them are under 18. Younger patients are usually at least 15, though she has operated on one 13-year-old and one 14-year-old, she said, both of whom had extreme distress about their chests. (https://www.nytimes.com/2022/09/26/health/top-surgery-transg...)
> Over the 3-year study period, a total of 204 gender affirmation surgical cases were identified: 177 chest/top and 27 genital/bottom surgeries (Table 1). Most cases were masculinizing chest reconstructions 177/204 (86.8%) with 65/177 (36.7%) of those patients being less than 18 years of age (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9000168/pdf/jcm...)
> The Komodo analysis of insurance claims found 56 genital surgeries among patients ages 13 to 17 with a prior gender dysphoria diagnosis from 2019 to 2021... In the three years ending in 2021, at least 776 mastectomies were performed in the United States on patients ages 13 to 17 with a gender dysphoria diagnosis, according to Komodo’s data analysis of insurance claims...A total of 17,683 patients, ages 6 through 17, with a prior gender dysphoria diagnosis initiated either puberty blockers or hormones or both during the five-year period. (https://www.reuters.com/investigates/special-report/usa-tran...)