I have never seen bald eagles around Ontario, Canada - but a couple of weeks ago Anne & I were driving on a country road and saw a large bird fly up from the road in front of us. Unfortunately, similarly to your situation - by the time we got to the area that it was in, it had flown to a treed place on the other side of a corn field well over 1/4 mile away.
I grabbed my camera and took this shot from my car window (heavily cropped from a pic taken with my 600mm lens), just to verify if it was a bald eagle or a vulture which are large and we see lots of them. I hope there is a possibility to come across one again. They are magnificent.
I too would love to capture a more closeup detailed picture of one. Also having better light. The image quality was further reduced by having to shoot in poor light at 6400ISO with a slow shutter speed of 1/100’th second with the lens wide open.