I have a KOA card for the discount because I stay at KOAs anyway. I have Good Sam Roadside Assistance and their Travel Assist for medical emergencies, but haven't needed either one. Camping World President's Club gives a discount in their stores and have a good selection. Actually, too good. I almost always leave with more than I went in for.
I have AAA for their travel guides and triptiks and their roadside assistance for my daily driver. My local office has people that understand the limitations of MHs and route accordingly. Their service people are independent contractors, so that's just dumb luck if you get a good one. Most don't have the equipment to tow a MH or change an RV tire.
I joined FMCA when I first started RVing, in part because I live about 4 miles from their home office. They cheerfully accepted my membership money even though I have a 'C', but the 'MC' stands for Motor Coach and their magazine makes that clear. Their big thing seems to be organizing group camping trips and pot lucks for their members which is fine if you like that, but I prefer to explore on my own. Different strokes...
The NPS's America the Beautiful Senior pass has to be the greatest thing since sliced bread, even if you don't camp inside. $10 lifetime pass if you're 62 or over, and it works at all NPS attractions.