In the United States, the equivalent would be a Southern Nationalist Party or a Southern Nationalist Caucus taking control of the state legislatures of, say, Texas, Alabama, and Tennessee and calling secession conventions.
“In Spain, the two pro-Catalan independence parties now control a majority of the regional parliament. While the Esquerra Republicana de Catalunya is on the political left and the Convergència i Unió is on the center-right, the one thing they can agree on is that Catalonia should be independent.
In Great Britain, the Scottish National Party has all but eliminated the Conservative Party north of the border and seats nearly twice as many members as the Labour Party in the Scottish Parliament. As for the United Kingdom herself, the United Kingdom Independence Party, derided by British Prime Minister David Cameron as a collection of “loonies, fruitcakes and closet racists,” just handed the Tories their Eton-educated heads in three by-elections that serve as a likely harbinger of political upheaval to come; UKIP has already effectively replaced the Liberal Democrats as the United Kingdom’s fourth most influential political party after the Conservatives, Labour, and the Scottish National Party. . .”
Note: It only takes two or three states in combination to force the issue.