As a Washington resident, I tested this a while back: nope, you can cancel online AFAICT (I didn’t actually cancel, but the click flow indicated that it should work), and do not need to be a CA resident.

IIRC they implemented online cancellation everywhere a while back.

I'm in Texas and was able to cancel online. It was slightly frictional. I had first paused my subscription. Apparently you can't cancel if your subscription is paused, so I had to reinstate the sub to cancel.

My Oklahoma-based subscription required chatting via text online with an agent to cancel.