It actually only requires the US alone to ban it. The cascading regulatory effect will force every bank in the world that deals in USD to also ban it automatically. Correspondence banking relationships in USD require all banks that want to use USD to follow US blacklist, sanctions, restrictions and rules as the money passes and settles ultimately via New York Fed and hence US has domain over all USD transactions globally. No international bank in the world will want to be cut off from USD or even be put on US blacklist.
Just watch if tomorrow US says bitcoin is banned. Every bank operating in USD will ban it also. They have no choice. No bank wants to end up like BOV in Malta having to use an indirect relationship to get access to USD via Raiffeisen bank in Austria....lol.
Iraq, Libya both tried to move away from dollar and it didn't end well. Iraq even asked US soldiers to leave Iraq recently after killing of Iranian General but US blackmailed them saying they will be shut out of dollar and all went silent
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WSJ News Exclusive | U.S. Warns Iraq It Risks Losing Access to Key Bank Account if Troops Told to Leave
You got to de-dollarize in silence like Russia is doing i.e offload your US Treasuries and smile in Trumps face but laugh behind his back...no open confrontation
. These US guys don't play fair. They will terrorise your financial system if you don't do what they say...lol....ask Turkey.