The European Commission has adopted a decision that recognises certain US venues as “equivalent” in regulatory terms with EU law. The decision document can be found here. The decision recognises that SEFs (Swap Execution Facilities) and DCMs (Designated Contract Markets) fulfil the 4 conditions found in MiFIR Article 28(4) and are therefore recognised as equivalent  from  the perspective of the trading obligation, which requires investment firms to execute the more liquid financial instruments on either an EU or equivalent trading venue.

This article on the Bloomberg web site also examines this issue.