Bergen : Complicating the Iraq picture is regionwide sectarian strife . He says the historic Lebanese -Shia split is a key dynamic and U.S. strike could worsen conflict . U.S. 's death toll from sectarian struggles has been increasing . Peter Bergen : Al Qaeda -affiliated groups will seek to take advantage .
Peter Bergen : Complicating the Syria picture is regionwide sectarian strife . He says the historic Sunni-Shia split is a key dynamic and U.S. strike could worsen conflict . Iraq 's death toll from sectarian struggles has been increasing . Bergen : Al Qaeda-affiliated groups will seek to take advantage .