"In practice, it would be quite difficult to do it, to start it would require, I think, a two-thirds majority of the FIFA congress, so the British would have to really piss everybody off to make that justification. Not that we're not capable of doing that, but we can claim that we have history on our side, traditions in soccer matter, so why would you abandon all of that history."
As for why no one in the U.K. has ever pushed for a single British team, and a chance to see Gareth Bale flying up the pitch and combining with Harry Kane in a World Cup match, Szymanski said that while, "The English would probably be quite happy to do that, because we're the big brother," having independent soccer teams means too much to the national pride of people from Scotland, Wales, and Northern Ireland.
"I would go as far to say, if FIFA actually did ever force Britain to field a single team, rather than have four home nations, the Scots would actually demand independence. They had an independence referendum a couple of years ago, which they lost narrowly, it would be overwhelmingly in favor of independence if they lost their soccer team, because that's the only way they'd get their soccer team back. And that would be easily important enough to the Scots, I have no doubt about that in my mind."
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Why England and other UK countries all have their own soccer teams
Brandon Wiggins
https://www.businessinsider.com/england-national-football-team-uk-great-britain-2018-6