It is bizarre to bring up China here, this isn't about the state dictating the payment system but maintaining a healthy market. It's like a garden, you don't dictate exactly how the plants grow, but you prune them once they encroach onto other plants to maintain a healthy balance.
I brought up Amex because it is common for merchants to not accept it, due to it being a significantly worse deal for the merchants. I am fine with the argument for an even more expansive version of my argument, but I'm making a more narrow argument due to discover, visa, mastercard being so close in how they function that it is not a burden on merchants to accept one vs the others.
To be fair, the core AMEX product is a charge card, not a credit card. They have more recently expanded into a few credit card products. I don't know the exact details, but my understanding is that the charge card system is more merchant hostile than the credit card system and more than simply larger fees.