its doubtful that theyd do a full-on ban, so they dont think there would be a black market for analog porn. what well most likely see is a ban on internet pornography. we already have age verifications in several states, so its not totally out of the realm of possibility. also the federal government shut down backpage and cl personals strictly on moral grounds (prostitution).  really any attempt will work. b-but muh vpns! muh peer to peer! doesnt matter. the credit card processors are in the us. the entire industry will be de facto demonetized when visa stops payments because the product is illegal. that means theres no profit associated with hosting so many free videos.
United States