Medical groups that support gender-affirming care (MSNBC graphic)

• American Medical Association
• American Academy of Pediatrics
• American Psychological Association
• Pediatric Endocrine Society
• American Society for Reproductive Medicine
• World Health Organization
• World Medical Association
• American Society of Plastic Surgeons
• American Academy of Child & Adolescent Psychiatry
• American Counseling Association
• American Nurses Association
• American College of Physicians
• USPATH (US Professional Association for Transgender Health)
• American Heart Association

I took the screenshot from this article:

The U.S. Trans Survey proves the inaccuracy of this right-wing talking point
Why you shouldn’t let the abundance of poorly sourced anti-trans rhetoric fool you.
Katelyn Burns, MSNBC Columnist
Feb. 12, 2024

Adversaries have portrayed this as a 'debate' since the 1970s

"And similar to the 1970s, opponents of trans medicine today frame gender-affirming care as a 'debate,' even though all major U.S. medical associations support these practices as medically necessary and lifesaving."
— Pseudoscience has long been used to oppress transgender people: Three major waves of opposition to transgender health care in the past century have cited faulty science to justify hostility. G. Samantha Rosenthal & The Conversation US. Scientific American. February 12, 2024.

Update: American Psychological Association

The APA has long supported gender-affirming care for youth. Now, they've also made clear that government shouldn't ban it.

On February 28, 2024, as Erin Reed writes, "the American Psychological Association announced in a historic policy resolution that it opposes gender-affirming care bans for transgender youth. The association, the largest psychological organization in the world with 157,000 members, declared, “Government bans on gender-affirming care disregard the comprehensive body of psychological and medical research supporting the positive impact of gender-affirming treatments,” and resolves the organization’s support for the necessity of that care for transgender youth and adults."

— World's Largest Psych Association Passes Policy Supporting Trans Youth Care By Massive Margin: The American Psychological Association, representing 157,000 members, has issued a resolution calling for an end to trans care bans and misinformation around care. Erin Reed, February 28, 2024.

Look at what evidence there is

"Cornell University has compiled over 50 studies supporting the benefits of gender-affirming care." (The Myth Of "Low Quality Evidence" Around Transgender Care, Erin Reed, August 8, 2023)