Unfortunately decoupling payments within the EU is insufficient if the US can just threaten to sanction your bank, and in doing so force the bank to drop you as a customer. Even in the presence of an internal European payments network, those banks still need to transact with the US and other US-sphere countries...

The US pressured Europe last time, in 2019, into aligning with their sanctions. https://en.wikipedia.org/wiki/Instrument_in_Support_of_Trade... The Iran situation could have gone better if trade and JCPOA nuclear oversight had continued.