I don’t know that I’d agree that the EU and the articles of confederation are comparable. There were a few big differences, including states printing their own currency without a common exchange medium (as opposed to the Euro), and that the mechanism for funding the federal government was (IIRC) entirely voluntary. States could just choose to not send money without consequences, and most or all made the obvious choice of not funding the federal government. The articles of confederation also had a few things about it that were more progressive than the constitution; for example, if I’m remembering right, it offered automatic citizenship to all native Americans, which pissed a lot of the farmer-settlers right off.