Marks, who has run the US PR team since December 2000, confirmed his resignation this week as a result of the review, which aims to merge Coke's corporate and North America PR functions and centralise communications.
He said the departmental reshuffle - part of a continuing drive to integrate Coke's domestic operating units - saw the firm slash six positions and reduce his role and responsibilities as US PR chief.
'This is part of an overall effort to centralise media relations,' Marks added.
He will return to GCI - from which he was originally recruited by Coke - as executive vice-president this month.
PR chief of Coke's Minute Maid unit in Houston Dan Schafer will now run the North America media relations team out of the Atlanta headquarters.
His staff, and the corporate comms team, will occupy the same floor for the first time.
In the past, Coke's media relations on issues of brand marketing were handled vertically by each product group, with relevant messages to the financial and global media handled out of the corporate offices.
A source inside the operation said Coke's external PR was heavily segmented, with little co-ordination across media groups.
The consolidation was described as an effort to more closely manage the influence news about Coke's US business has on the rest of its operations.
Marks's return to GCI coincides with a number of changes at the agency.
Cohn & Wolfe founder Bob Cohn has resigned as chairman of GCI Atlanta to launch a new agency, taking several GCI staff with him, including senior vice-president Jim Overstreet and chief marketing officer Amy Parrish.
The agency, Cohn Overstreet & Parrish, opens with clients including the US Army Reserves.