USA has cast the two leads of its upcoming ?Bourne? spinoff series ?Treadstone,? the network said Thursday. Jeremy Irvine, who recently played a young Pierce Brosnan in ?Mamma Mia! Here We Go Again,? will play J. Randolph Bentley in the series, a spy dispatched by the CIA to eliminate a key target, but ends up embroiled in an international conspiracy. ?Sense8? alum Brian J.