As far as we know, Tiktok is operated on US servers by Oracle. While it might have been possible to find another cloud provider and move all US data there, I can see them not wanting to do that given that there was no point if the app isn't distributed in the US anymore.
From (2)(a)(1):
> (A) Providing services to distribute, maintain, or update such foreign adversary controlled application (including any source code of such application) by means of a marketplace (including an online mobile application store) through which users within the land or maritime borders of the United States may access, maintain, or update such application.
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> (B) Providing internet hosting services to enable the distribution, maintenance, or updating of such foreign adversary controlled application for users within the land or maritime borders of the United States.
Possession of and providing non-distribution ( / maintenance / update) services to a "Foreign Adversary Controlled Application" are not in any way a part of the "Protecting Americans from Foreign Adversary Controlled Applications Act". Operative services are specifically and intentionally excluded from the list, to ease the burden of enforcement.