Often, you can remove the one screw then rotate the entire cleat, which may help take the screw with it. Other wise grind or cut the cleat to where you can break it out from under the bolt, which does to things. It gives access to the head so you can use a pair of pliers, and takes the tension off the screw, which by itself is often enough.

Obviously this sacrifices the cleat, but if you don't need to replace it anyway, you might as well leave it alone until you do.

Cleat screws tend to be good candidates for binding, because they see all kinds of weather from the bottom, and are vulnerable to your own sweat wicking in from the top. I always mount cleats using a good, waterproof MoS2 grease, and so far have done OK. (of course that could just be good luck, and not the grease).