Actually... I've been doing some digging and that doesn't sound like it's the case. I think it just makes it illegal to host the services in the us and provide the application from us services like app stores..
(1) PROHIBITION OF FOREIGN ADVERSARY CONTROLLED APPLICATIONS.—It shall be unlawful for an entity to distribute, maintain, or update (or enable the distribution, maintenance, or updating of) a foreign adversary controlled application by carrying out, within the land or maritime borders of the United States, any of the following:
(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.
(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.
No there would be no blocking the would just shut it down but the could sanction any company that violates the ban that's about it for enforcement. But a VPN to another country would bypass it but it would not be US version of tiktok.