Brexiteers should have been prepared for the shattering intervention of the US. The European Union always was an American project.
It was Washington that drove European integration in the late 1940s, and funded it covertly under the Truman, Eisenhower, Kennedy, Johnson, and Nixon administrations.
While irritated at times, the US has relied on the EU ever since as the anchor to American regional interests alongside NATO.
There has never been a divide-and-rule strategy.
The eurosceptic camp has been strangely blind to this, somehow supposing that powerful forces across the Atlantic are egging on British secession, and will hail them as liberators.