They already support local payment processing schemes such as Bancontact, iDEAL, JCB, Pix, etc. A good chunk of their international customer base already isn’t dependent on the big American payment processors.
The way towards undermining Visa/MC’s power is for more governments/Central Banks to push for indigenous alternatives which abide by local regulations rather than foreign puritanism. This is already a desirable goal for most both from a geopolitical POV (reduce American control over world finance) and a financial one (VISA/MasterCard charge outrageous transaction fees).
American consumers are fucked whichever way things go though, it’s not like the regime is going to make a move to break up the monopoly nor to push for less censorship in media. If Valve somehow goes through with this and makes deal with all major American banks, they’ll be done just in time for the Save The Children From Pedostanic Video Games Act or whatever the fuck that will force them to purge all thought crime from their platform.
Weird, either there’s some backroom drama with Interac or now might be the time for you to ask their support about it.