We had a thread devoted to collusion just a couple of weeks ago.
USA has not had a comparable terrorist war to draw comparisons.
In the Indian wars, government colluded with prospecters and others to break treaties protecting Indian lands, and in the extermination of the buffalo.
The well armed mobsters of the 20s and 30s were a kind of terroris.
Collusion within local government and the police was absolutely rife.

SinnFein worked in close co operation with PIRA, so you could say that Sinn Fein politicians colluded in most or all PIRA murders.