Europeans being turned against each other - and specifically English people being turned against Germans - is what the powerful right-wing forces in the US dream of, as it quashes any kind of hope that the EU might be a great power in itself, no longer dependant on US backup.
The upsurge of English nationalism which would follow an England win - that may seem unlikely, but never underestimate the ability of English players to play above themselves against the country they have mostly been brought up to despise - might make it almost impossible for millions who know no other land to live in England, quite apart from the push it would undoubtedly give to Scottish separatism (already boosted by the election, of course) and the ethnic-nationalist-led chaos that would cause in England.
I would not rule out the possibility that the CIA fixed the USA game on the (as it turned out, correct) assumption that Germany would beat Ghana. Even if they didn't, I knew from the moment that goal went in that Germany would win. The USA couldn't prevent England playing Germany. It would have refuted everything they want the most.
The pre-history of ethnic cleansing in England might decisively begin today.