What are the AMA's responsibilities for Pro MX and SX?

They come up with the naming of the classes

A "sanctioning body" refers to an organization that officially approves and regulates a specific activity, often within a sport or industry, and has the authority to enforce rules and regulations. They essentially act as a governing body, providing oversight and guidance.

Source: AI

To do what ever

FULD and MX spurts tell them  

AMA has been bought plain and simple  

Need new sanctioning body that PRO rider NOT promoter 

“The American Motorcyclist Association (AMA) is a non-profit organization that promotes the motorcycle lifestyle and protects the future of motorcycling. They advocate for motorcyclists' rights, organize various events and activities, and provide resources and benefits to members.”

I guess motocross riders and tracks don’t fall into that category but at least we get that really cool and up to date magazine every month, right fellas?!?!

Ban 250 2 stroke vs 4 stroke racing in the pros

The direct answer is the AMA has limited relationship to Pro MX or SX 

American Motorcyclist Association not the same as AMA Pro Racing, who oversees ProMX and SMX (as well as AFT, ATV MX, and Hilclimb): 

AMA Home - American Motorcyclist Association

AMA Pro Racing - the rule book for Pro MX and SMX is here

And AMA Pro Racing was sold to DMG who leases the rights to AMA Pro Motocross to MXSports who uses an AMA Pro Racing Rulebook, as opposed to Feld who has the rights to AMA Supercross and uses an AMA Rulebook. So, like, it's complicated. lol

Sounds like a Ponzi scheme 👌

Who knows anymore?

provide certain services, sign up, tech inspection, sound test, points, etc

Responsibilities include stalking me for yearly dues 5 months in advance, then send updated card out  in a couple months.

Collecting sanctioning fees, not properly enforcing the rules and ignoring the sport. 

Issuing penalties for the same things that FELD uses to promote SX. 

If they get one of those guys pregnant they have to marry him.