The teenager has already competed in 13 professional matches for New York City's senior team.
Along with MacFarlane, City also have an agreement for Philadelphia Union's superkid Cavan Sullivan, 15.
Transfer expert Fabrizio Romano is reporting: "Manchester City will sign 2007 born talented left back Christian McFarlane in January 2025, deal sealed as expected.
"Man City Academy and City Football Group to bring in another huge talent as from US after Cavan Sullivan."