TechLand isn’t worth the FTC trying to use its clout, especially since the Treasury Department has already blocked action against Tencent previously. It would make the FTC look like fools if they tried to use their clout outside of their jurisdiction and were shut down not just by China, who would love to make the US look foolish in any way, but also by their own government.
The UK is using their clout outside of their jurisdiction on a much more significant market disruption to their own country and in the jurisdiction of a mostly cooperative ally.