Coal power plants are at least twice as bad as natural gas power plants depending on how you measure such things. CO2 is much less. Other pollutants definitely less as natural gas burns a lot cleaner.So 60% fossil fuel. I didn’t realize there was still so much nuclear energy produced in the US. Most of the nuclear plants around here were shut down decades ago and the last functioning nuclear plant is supposed to be shut down soon, although (leave it to California) they are taking too long replacing the generators with clean alternatives. Source
See why I am worried about full electric in California by 2035? California moves at a snails pace.
Now it's definitely not perfect but lumping them together doesn't make sense.