It seems Itch removed the credit card payment option from all games with NSFW content due to a request from the company that manages that payment, and there's no indication that this will change.
Another possibility is that the game developer themselves changed the payment method to "direct to you." In that case, it's the developer, not Itch, who determines whether the game can be purchased by credit card and/or PayPal.
PS: You might not know this, but PayPal works almost everywhere in the world; you don't need to live in the US to open and use a PayPal account.