Well, this will add more frustration for Armorcast and customers from Austrailia as well as more nations listed recently below:
As of September 3, 2021, USPS has temporarily suspended FCI Package shipments to Australia. To avoid disruption, use Priority Mail International or GlobalPost Standard to ship your packages.
Further research shows this from www.usps.com:
International Mail Service Suspensions
Updated: Sept. 7, 2021
The Postal Service™ is temporarily suspending international mail acceptance for certain destinations due to impacts related to the COVID-19 pandemic and other unrelated service disruptions.
Updated: Nov. 22, 2021
Suspension Due to Unavailability of Transportation
Saint Pierre and Miquelon (Miquelon)
Customers: please refrain from mailing items addressed to the countries listed here, until further notice.
These service disruptions affect Priority Mail Express International® (PMEI), Priority Mail International® (PMI), First-Class Mail International® (FCMI), First-Class Package International Service® (FCPIS®), International Priority Airmail® (IPA®), International Surface Air Lift® (ISAL®), and M-Bag® items.
*Australia’s service disruptions affect First-Class Package International Service® (FCPIS®), Commercial ePacket (CeP), International Priority Airmail® (IPA®) packets and International Surface Air Lift® (ISAL®) packets only.
Unless otherwise noted, service suspensions to a particular country do not affect delivery of military and diplomatic mail.
For already deposited items, other than GXG:
Postal Service employees endorse them “Mail Service Suspended — Return to Sender” and then place them in the mail stream for return.
For any returned item bearing a customs form:
The Postal Service will, upon request, refund postage and fees on mail returned due to the suspension of service.
For all other returned items not bearing a customs declarations form:
The Postal Service will, upon request, refund postage and fees on mail returned due to the suspension of service, or
The sender may remail them with the existing postage once service has been restored. When remailing under this option, customers must cross out the markings “Mail Service Suspended — Return to Sender.”