It seems like NOAA used to provide sunshine data from the US weather stations but no longer does. Is there a reason that was discontinued?
It was not discontinued
Using the Climate Data Online tool from NOAA's website, I was able to get sunshine data through March 1st of this year for both major airports in my metropolitan area.
Sunshine data is relatively restricted geographically compared to other datasets like temperature and precipitation (for those I counted 7 stations in my metro area), but you should be able to retrieve data from any major airport.