The AUMF was an addition to WP so Iran's lack of support for AQ doesn't limit normal WP operations. Additionally sectarian concerns are more malleable than presented. As an example review Iran's long-standing support for Hamas which is Sunni-affiliated.

  —Consistent with section 8(a)(1) of the War Powers Resolution, the Congress 
  declares that this section is intended to constitute specific statutory 
  authorization within the meaning of section 5(b) of the War Powers 
  Resolution.