I majored in ultrasound in China. How can I be transferred to the United States as a technician?

You can get a master's degree in vocational entry and take a local license after graduation. However, this course is generally designed for people who want to change careers after graduating from science and engineering. There must be a lot of courses you have taken, which is a bit of a waste of time, and your visa may be stuck. (unlikely, but possible)

If you have the conditions, you can also find a work visa before you get a certificate. It's hard to find without photos when there are people here, but you can try. I know a person who has had radiotherapy in this way. I think the ultrasound diagnosis should be about the same.

If you have a green card, your job prospects are good, but it is not as good as radiation and X-rays. But generally speaking, there is a shortage of medical and health technicians in the United States, which is why it is not easy to get a visa. It's easy to find a job in this line. Immigration is easy, and the visa officer is afraid of your immigration.