(Holding my nose, and wading into the mudfest....)
Am I missing something here? All of these events are originated, organized, hosted, etc. by local groups. The AMA provides sanctions, primarily to keep events from impinging on each other. And, of course, specific insurance binders if needed for an event. But they ultimately have almost no control over whether any event is held, or not. It is each group that has the responsibility to hold/not hold their event. Since the AMA issued their advisory about six hours before this thread started, it seems they have done what would be expected - issued reminder advice to the various events, and in a time frame earlier than many other organizations, including government bodies. The onus has always been on the individual event organizers - they are the ones that have the direct responsibility to ensure public safety.