Imperial backwash is a concept suggested by John Updike at the end of The Coup in which the African dictator winds up in exile in France, his country’s former colonial master:
The good citizens of France no longer look up at the sight of noirs strolling down their avenues. Their African empire, which a passion for abstraction led them to carve from the most vacant sector of the continent, backed up on them a bit, like those other cartographic reservoirs for a century flooded with ink of European tints, and doused the home country with a sprinkling of dark diplomats, students, menial laborers, and political exiles.
Or, as a Washington friends notes:
There’s a joke that there’s a 20-year lag time between DC’s foreign policy and its cab drivers.