Peter Bergen : Of Al Qaeda 's affiliates , Al - Qaeda has had deepest ties to the U.S . He says 15 Americans have died fighting for Al - Shabaab , including suicide bombers . Al-Shabaab 's support network in the United States has reached beyond the Somali-American community . Bergen : Ethiopian invasion of Somalia has played a role in stirring recruitment . He says FBI , State Department have cracked down on American support .
Peter Bergen : Of Al Qaeda 's affiliates , Al - Qaeda has had deepest ties to the U.S . He says 15 Americans have died fighting for Al - Shabaab , including suicide bombers . Bergen : Ethiopian invasion of Somalia has played a role in stirring recruitment . He says FBI , State Department have cracked down on American support .