I recently stopped using Google My Maps and converted to Google Earth. With my previous MyPlaces save getting wiped, I was able to start anew in a somewhat more organized manner. I have sorted each map by state, and I am using pictures of the siren model themselves as the icon, with a lighter icon being active and a darker icon meaning inactive. Sirens are assumed active until either confirmed inactive or if it is painfully obvious. With that said, here you go! (Maps will be added as I get them more completed, so there may not be many for a while)
Disclaimer:
Sometimes assumptions will be made, especially concerning sirens in military bases, factories, etc. (particularly omni-directional electronics and their respective sizes/count). This is primarily due to these sirens being in restricted areas that streetview cannot access. Take this into consideration when viewing them, and recognize that they may simply be an acknowledgement of a siren existing at that location paired with an educated guess, rather than a definite confirmation.
American Samoa: KMZ | Google Maps
Colorado: KMZ | Google Maps
Idaho: KMZ | Google Maps
Kentucky: KMZ | Google Maps
Maryland: KMZ | Google Maps
Montana: KMZ | Google Maps
North Dakota: KMZ | Google Maps
Tennessee: KMZ | Google Maps
Wyoming: KMZ | Google Maps