Flood insurance is a national program underwritten by FEMA. We have it on our house in inland New Jersey, because we're on a river.

You may be thinking of the windstorm insurance program. The state of Florida underwrites that, and started it as insurance of last resort after insurers started bailing following Andrew.

Possible. The point was that people kept building mansions in clearly unsuitable areas and when the private market wouldn’t insure them they made the government do so.

This is the case pretty much everywhere, and is unrelated to sea level rise.