1. I am in the US, and can access the buy option with card without issue
2. This is currently on sale on Steam
it's not a card issue, it's a way of protest since a lot of works have been banned/shadowbanned (my own too!) due to pressure from christian nationalists like the original poster said. steam is doing the same, this is more of a visa/mastercard issue (though steam and itch are bending to their requests)