The Global Corporate Congress (GCC) is the corporate controlled government of the North American Union and consists of the many CEOs of the largest corporations in the future.
Judging from Kiera's statement that Piron is one of the biggest 20 corporations in 2077, the Corporate Congress may be composed of 20 members.
Cameron states in "Revolutions Per Minute" that not every member of the Global Corporate Congress in 2077 existed yet in 2014. For example, at that time SadTech was just an idea for a startup company that young Alec Sadler had. In Cameron's original timeline, Piron didn't exist in 2013, but Mr. Escher started it up years earlier using time travel. Some of the other corporations did exist by 2014 but were still relatively small companies, such as LaRoche Energy or Gautuma Medical, which would only grow into giants decades later after they developed revolutionary technological breakthroughs. Other companies were already large mega-corporations by 2014, such as Sonmanto, Fermitas, and Vickerdale Enterprises.
In 2076 it was bombed by Liber8. This bombing caused the death of 30,000 people in hopes of killing the 20 members of the Corporate Congress.
In "Final Hour" it was revealed by Older Alec to Keira in the improved 2077 that GCC was never formed. There was no collapse, no uprising, no revolution. No corporate congress. Julian and Edouard and he saw to that.