Yes, exactly. The Europeans have the required reputation to create their own system for the EU countries at least, but I doubt it would extend to non-EU countries anytime soon. The BRICS has tried to create such an interbank system but it hasn't happened yet, due to lack of political will as you said.
Yes, if I'm not mistaken, Iran tried to integrate with UnionPay as well, but China wasn't interested, probably because of the US sanctions. But Iranian ATMs accept Russian MIR cards now. Iran's SHETAB cards are now accepted in Russian ATMs as well. I think Iran is also in talks with Belarus to do the same.
Iran has multiple payment systems. For ATMs, it's called SHETAB, which is an acronym but it is also the literal word for 'acceleration' in Persian. It is the fastest payment method in Iran and transactions are processed immediately and it works 24/7. All debit cards issued by banks in Iran are connected to SHETAB by default.
We have other systems for larger amounts of money called PAYA and SATNA. Their transactions are processed in prescheduled intervals. There is also another payment system called POL, which is like SHETAB but it's used for larger amounts of money and only some Iranian banks support it.
These are the major level-0 systems in Iran, but several payment gateways offer different functionalities based on these systems, which are indirectly controlled by the Central Bank of Iran. The payment gateways have their own APIs for other websites. Sort of like Stripe.