It’s open source, and Australia and Canada have both deployed instances. Would love to see a US (or state run) instance.
United States Alert Message Service as a branch of USPS?
You’d want it under the authority of GSA (like Login.gov), as a foundational service (messaging.gov).
"if you work in central government, a local authority, or the NHS."
Reusable open source components all governments can use is still a huge improvement over the status quo, where each government overpays contractors to build suboptimal solutions that remain closed source.