Yet despite promises of a “whole of government” effort, key agencies — like the Army Corps of Engineers, other parts of the Defense Department, the Federal Emergency Management Agency and the Department of Veterans Affairs — had not been asked to play much of a role.

Even after Mr. Trump committed to supporting the states on Tuesday, the Army Corps of Engineers said it still had not received direction from the administration…

Much of that capacity is untapped. Hospital ships are at port. The Department of Veterans Affairs, legally designated as the backup health care system in national emergencies, awaits requests for help. The veterans department has a surplus of beds in many of its 172 hospital centers and a robust number of special rooms for patients with breathing disorders.

The sprawling system of emergency doctors and nurses ready to be deployed by the Department of Health and Human Services — known as the National Disaster Medical System — is also still waiting for orders, other than to staff locations where passengers offloaded from cruise ships are being quarantined.