Just being an ambassador like you are, and JOINING BRC and whatever else makes sense to you, IS DOING your part. Awesomeness.
It is the least I can do. Here in Ohio, there are no roads available for exploring other than a couple dozen miles in the extreme SE corner. So no clubs other than mudder clubs in someone's field, no advocacy, and no state organizations that I've found.
When hiking over the last several decades, I've always picked up other people's trash and packed it out in my Klettersack. It's how I was raised, and a backpacking mantra. But since joining Overland Bound, my awareness has been increased, and over the last year, I've made contributions to Tread Lightly, Leave No Trace, and now BRC. Membership is a drop in the bucket compared to what we spend on toys and gear, and like I said, it is the least I can do!