2011 Mercury Marquis brake fluid level in reservoir

I believe my brakes were dragging a bit on a road trip today. At first I thought it might be the transmission slipping but I remember thinking that my brake pedal was nearly to the top when I depressed it. My reservoir is above the maximum line, in fact, it is up to the neck of the reservoir. I'd like to know if this overfill could have caused my brakes to drag. I checked it as soon as I got home when the fluid would still be heated. I have removed some of the fluid down to the "max" level. I might say the reservoir sits at a bit of an angle, not level, so checking the level is somewhat uncertain.
Thanks in advance for your response.
Sandy