That was an irrational, knee-jerk reaction by the Americans. The man did not get radicalized in Nigeria. It happened in England, where he went to university.
England is a cesspit. England is the breeding ground of fundamentalist Muslims. Its social logic is to allow all religions to preach openly. But this is illogic, because none of the other religions preach apocalyptic violence. And yet England allows it.This is part of the character of Great Britain. Colonialism bred an innate arrogance, but when you undertake that sort of imperial adventure, that arrogance gives way to a feeling of accommodativeness. You take pride in your openness.
This demonstrates, I believe, the ontological impossibility of declaring "war" on terrorism.