Guess which state is opting out of energy-savings rebate program because it’s ‘woke’
(www.miamiherald.com)
Flood insurance is provided by the NFIP, mostly, which is a federally run program by FEMA. The cost may be prohibitive in some areas due to the frequency of flooding unless mitigated but they will write anywhere.
That said communities can choose to not participate in the NFIP and as such flood insurance with the NFIP will be unavailable. (Maybe this is what you are referring to?) There are also some coverage limitations as far as maximum amounts, $250k building & $100k contents, they will cover that can require you to seek excess flood insurance from private companies.
There are private flood insurance companies as well but nearly everyone gets at least the first layer of coverage from the NFIP and uses private companies for excess.