Inquiries like this are more likely to draw useful responses if you say what sort of use you have in mind. Footpaths, for example, are really different from trails on which you can ride a bike, ride a motorcycle, or drive a four-wheeled vehicle. Also be aware that asking about local "rights of way" is likely to confuse, as will "green laning" "trekking," or other non-USA euphemisms; just ask about trails for walking/hiking if that's what you're after, or for off-road vehicle (ORV) use, or for mountain biking, or for whatever else as applicable. In the end you'll have to inquire locally anyway, noting that these are separate constituencies and often bitterly opposed to each other's interests.

I don't know anything about the British maps you reference, but as a fellow paper map user I have a few US suggestions which may meet your needs--or not. I find each of the following useful, but each also quite frustrating for their limitations.

The Atlas and Gazatteer series, now or formerly published by DeLorme.
The Road and Recreation Atlas series, n/f by Benchmark Maps.
The US Geological Survey (USGS) maps, in particular the 15 minute quadrangle series, [Beware: these are incredibly detailed but often painfully out of date].
The Trails Illustrated, now owned by the National Geographic.
The Green Trails series

Most people use online or similar maps these days. In my area, mountain bikers use the Trailforks app, but hikers might prefer Avenza, Maps.me, or Caltopo. In central California they may use apps I've never even heard of. I've found that paper resources are increasingly hard to find and dated, so I end up using apps to keep my paper maps updated.

Note that I know nothing whatsoever about the San Luis Obisbo area. Nonetheless, I hope that's helpful.

Mark