The altercation happened during Saturday’s U. Open final.
The cartoon has been condemned as racist by civil rights leaders, celebrities and fans.
She also said he treated her differently than male players during her loss to Naomi Osaka.
Williams was handed three code violations — and docked a point and then a game — in her 6-2, 6-4 loss to Naomi Osaka in the Flushing Meadows final
Naomi Osaka became the first Japanese to win a Grand Slam singles title on Saturday as her idol Serena Williams angrily imploded, calling the chair umpire in the US Open final "a thief".