IAAD. Most of these points on medicine are either outdated or plain inaccurate.
1. The AMA had tight control on med schools 50-100 years ago. These days a mediocre score on the MCAT and a desire for $300k+ in debt
will get you into a for-profit medical school. More DOs match with MDs, there are more foreign IMGs, and even US med school slots have grown in the past 10 years. The (over)supply of med students is a non-issue in 2019 except for the aforementioned bag holders that really had no business in med school.
2. Since the 60s the AMA continues a slow decline in relevance. Less than 25% of MDs in the US are AMA members. I was an AMA member. Why? Because they bribed me and my classmates with significant discounts on exam prep material. At some point there will be more student members than practicing physicians.
3. The AMA may be aware of pediatricians vs. cardiologists, but they have little to do with it now. One, the over-abundance of cardiologists isn't an indisputable fact. Regional maldistribution is a thing. There are many parts of the US where a cards referral will still take months. The AMA is not the reason pediatric specialities have relatively poor compensation relative to years of training and lifestyle. The ACGME and other interest groups, even big pharma, device manufacturers had much to do with setting the stage. These days, large organizations help maintain the status quo.
Consider that pediatric subspecialties are not competitive. Just about any average to slightly below average US grad that wants to do it can... it's not a labor supply issue!
In 2019 some doctors have it pretty good, and some not so much. Geographic disparities are huge. The public policy affecting medical practitioners is now a large number of independent special interest groups and public policy wonks. For instance, cardiologists have the ACC (their own body), but what is really powerful at this point is the motley group of pharma companies and interventional device mfrs, and huge HCOs... practitioners can benefit because obviously some interests align (A TAVR isn't too profitable without a doc to place it).
tl;dr medical professionals sort of bounce around in a Medusa head of healthcare organization and industry special interests these days... we're doing well insofar as we are useful idiots in this machine. The idea that we have unified representation is laughable.