Where is the 'Muslim world'?


I read this about an alert the United States announced:-
    The United States is shuttering its embassies and consulates throughout the Muslim world on Sunday after receiving an unspecified threat, officials said...they were taking action out of an “abundance of caution.”...
    Other U.S. officials said the threat was in the Muslim world, where Sunday is a workday. American diplomatic missions in Europe, Latin America and many other places are closed on Sunday.  Those officials spoke on condition of anonymity because they weren’t authorized to speak publicly about the matter.
and I wondered.  
Would this be considered a paternalistic racist attitude (a la Edward Said''s orientalism) in that that embassies and consulates in other places outside the "Muslim world " will remain open?
After all, aren''t there Muslims all over the world?  Even in ... Boston?
Where is this ''Muslim world''?  Where is it not?