Here are Ham's fears, stated sometime ago, that al-Qaeda and al-Shabaab link is dangerous for the US as well.
"If you ask me what keeps me awake at night, it is the thought of an American passport-holding person who transits through a training camp in Somalia and gets some skill and then finds their way back into the United States to attack Americans here in our homeland," General Carter Ham, the head of the United States Africa Command, said late last year.
That link is somewhat more formal and confirmed now.
News that Harakat Al-Shabaab - long associated with al Qaeda but never formally welcomed into the family - has gotten the blessingp from al Qaeda's leader seems to be a merger that was a long time coming. But the announcement does raise concerns that that the Somali terror group could help them in plotting to attack on U.S. soil.
Both of the above quotes come from the same link.
http://security.blogs.cnn.com/2012/0...-new-concerns/