Indeed - Payment companies like Visa and Mastercard enforcing American cultural and religious conservatism on other countries and nations is an illegal situation - per other countries' laws.
These are effectively monopolies. It doesnt matter whether there's two of them. If they collectively enforce something onto the people of other countries - like Europe - then they are violating those countries' laws
They must be investigated and regulated accordingly in Europe. American culture and American laws do not apply to Europe.
One of the reasons why this happens is money and specifically money from pension funds. The largest pension funds nearly all have "morality clauses" with them and won't invest with an entity that goes against that.
The other portion of this is the hassle of dealing with the adult industry in terms of politics. You can Google to see how the news articles came out claiming PornHub was being used for pornographic material related to children. Visa & Mastercard from public pressure revoked their ability to process any payments on that site. Canadian House of Commons Ethics Committee did hearings against the company. Nobody wants that kind of attention.
These are effectively monopolies. It doesnt matter whether there's two of them. If they collectively enforce something onto the people of other countries - like Europe - then they are violating those countries' laws
They must be investigated and regulated accordingly in Europe. American culture and American laws do not apply to Europe.