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Passing the background check is the problem EJ, the FBI'ts have gotten real testy since 9/11. Blanket overall rejection since overseas references you cannot trust.
Exceptions do exist, say you worked with MI5. MI6, SAS, or similar in the UK no problem. Germany is a blanket rejection, their services are lousy with Russian Intelligence; GRU or FSB. Swiss probably, their internal security top drawer. The list is amusing to look at at times