Huh? Article 50 is still there, and isn't a UK specific thing: https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX%3A12012M050 https://eur-lex.europa.eu/

Huh? Article 50 is still there, and isn't a UK specific thing: https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX%3A12012M050 https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX%3A... "Any Member State may decide to withdraw from the Union in accordance with its own constitutional requirements." Wikipedia (at https://en.wikipedia.org/wiki/Withdrawal_from_the_European_Union#Background https://en.wikipedia.org/wiki/Withdrawal_from_the_European_U...) notes that a formal method of leaving became a thing in the early 2000s when various Eastern European states were joining, not when the UK joined in the 1970s. (As for the US, I did say actually passing a constitutional amendment to allow succession would be unlikely, but I don't think it's legally impossible?)