Let's be clear: the EU was not set up to promote a friendly big socialist community, a Soviet-lite. The EU was created by the US, originally the European Coal and Steel Community set up in 1950 with the intent of promoting European integration, approved by Truman as a Cold War anti-domino measure. The chief method of promoting compliance with the US-sponsored post-war order was through provision of aid. The Marshall Plan (1948) was the vehicle for Europe, aid tied to the purchase of US goods and services, effectively subsidizing the US balance of payments.
The main international organs created at the time to regulate international economic matters—the World Bank, the IMF, GATT—and the Marshall Plan for European reconstruction were rejected by the Soviet Union as part of US imperial plans. Which of course they were, since it is only rational that the US as chief architect of the post-war international system would set rules which would allow it to win. The US Senate rejected US participation in the British-designed League of Nations, rightly seeing it as an infringement on US sovereignty, but voted 89–2 for membership in the clearly US-controlled UN in 1945.