IMHO – The linguistics are interesting.  The accent he’s using is a combination of British (central London – West end) and American.  The underlying accent -the dominant one- is definitely upper Central North American.  However, there is a surface English dialect noted layering the original. 
(Not New Jersey, Not New York or New England either.  More like Central Upper Mid-West)  Given the number of Jihadists in/around Minneapolis Minnesota that would be my best guess.  Chicago Illinois second, and then a stretch would be Miami FL third.
The FBI is asking for the public’s help identifying individuals who have traveled—or are planning to travel—overseas to engage in combat alongside terrorist organizations.

“We need the public’s assistance in identifying U.S. persons going to fight overseas with terrorist groups or who are returning home from fighting overseas,” said Michael Steinbach, assistant director of the FBI’s Counterterrorism Division.

The FBI needs your help identifying the individuals in this video as well as anyone traveling abroad to join terrorist organizations. Please send tips to www.fbi.gov/ISILtips or call 1-800-CALL-FBI (1-800-225-5324) with information.  (link to more data)
Again, because of the layered accent it would appear the most recent social surroundings would be U.K.   Maybe he left the U.S. for England prior arrival in Syria. 
Your thoughts ?