Updating payment method

The options for updating the expiration date are grayed out (not functional) and when I try to remove that card and add another it won't let me saying that family sharing requires at least one payment method. When I simply try to add another payment method I get nowhere, the system doesn't respond at all to that command excpt to give me a long list of payment option by country. I know a commercial US based credit card is an acceptable option. I've had this problem for awhile so I've stopped using iTunes but I need an app on my iphone and even though the app is free it won't download, it just tells me I have to update my payment method. This "do-loop" problem (did that phrase just give away my age?, haha) is maddening.