Don't you mean, all Amazon sales to customers in the state who buy something on Amazon by way of a link from a California-based affiliate's website are subject to the tax (or would have been, if Amazon had not cut them loose?)
.....by way of a link from a California-based affiliate’s website ...
I don’t know about that. I think an affiliate bookshop for instance that sells a book via the Amazon site listing would trigger the California presence even if they had no website of their own.
I recently bought a used volume from a California seller listed as one of several sellers on the Amazon site. That seller is now not an Amazon affiliate by my understanding of the situation.