I think I went a little too far filling my car up with gasoline and now my car is having trouble accelerating. Sometimes I hear pops coming from under the car when I push the pedal harder so I can actually move.
Did I screw up my car?
It’s a used 1998 Ford Escort.
Probably just coincidence that the problems showed up about the same time. The only ill effect I’ve ever seen from overfilling a gas tank is gasoline getting all over the side of the car and the ground, and my hands smelling like gasoline for several hours.
…not to mention money spilled on the ground! 
There’s a charcoal canister that’s designed to trap gasoline vapors before they can escape into the air. In some cars, under some conditions, overfilling the gas tank can force the liquid gasoline up into the canister, soaking the charcoal and rendering it useless.
I don’t think, however, that it would actually affect how your car runs.
Of course it matters. It’s a pressurized system that requires equilibrium.