Would it be possible to get a list of all public sensor coordinates, say within the continental U.S.?
Yes and no. We have a feature called a Bounding Box API Call where you use the northwest and southeast latitude/longitude points of your desired coverage area and data from all sensors in that area will be returned. More details about the Bounding Box API Call can be found here: Finding Large Amounts of Sensor Indexes (Bounding Box API Call).
Currently, there is no way to obtain sensor indexes using the API based on national or provincial borders. We will be adding this feature to our system in the near future. If you would like, we can give you an update when that happens.