Would it be possible for FEMA to have just gone on their own accord on the ground that any reasonable Secretary of Homeland Security would have asked them to go?
This is correct, as a federal entity, FEMA will only show up after being invited by the governor of the state that needs assistance. Thats why search+rescue is usually handled by local authorities and FEMA focuses on clean up, logistics, and rebuilding. This does not exclude them from assisting with S+R, but they will almost never be the first ones on scene.
Would it be possible for FEMA to have just gone on their own accord on the ground that any reasonable Secretary of Homeland Security would have asked them to go?
No
This is correct, as a federal entity, FEMA will only show up after being invited by the governor of the state that needs assistance. Thats why search+rescue is usually handled by local authorities and FEMA focuses on clean up, logistics, and rebuilding. This does not exclude them from assisting with S+R, but they will almost never be the first ones on scene.