That isn't signing up, that is filling out a profile and/or stating/proving who you are (for payment processing & fraud prevention purposes). While it is often closely linked to “signing up” it is not actually a direct part of it.

Even if you consider it all to be part of the sign-up, it could be a single form so the match of “as many forms to cancel as to sign-up” still works: this one form for signing up, the “are you sure, this is why you might prefer not to” page being its opposite at the other end.

They don't have to, they can just do fewer or the same that it takes to sign up. Better yet, we could require "one-click unsubscribe". It's our country and we get to choose to make it better.

I agree, that would be super annoying, but at the same time the law would still be mostly working this case, since you still don't need to eg fax a form or have to get on a long phone call. I think "the effort you need to sign up" is a reasonable ceiling, and while it's unfortunate if a company decides to be petty and make you enter your address again, that same company would probably do more if they were given the legal right to do so.