The FCC maintains a list of equipment and services (Covered List)
that have been determined to “pose an unacceptable risk to the
national security
Recently, malicious state and non-state sponsored cyber attackers
have increasingly leveraged the vulnerabilities in small and home
office routers produced abroad to carry out direct attacks against
American civilians in their homes.
Vulnerabilities have nothing to do with country of manufacture. They have always been due to manufacturers' crap security practices. Security experts have been trying to call attention to this problem for 2 decades.
Manufacturers have never had to care about security because no Gov agency would ever mandate secure firmware. This includes the FCC which license their devices and the FTC who (until recently) had the direct mandate to protect consumers.
Our most recent step backward was to gut those agencies of any ability to provide consumer oversight. All they they can do now is craft protectionist policies that favor campaign donors.
The US has a bazillion devices with crap security because we set ourselves up for this.