A difficult or embarrassing problem or situation. A pitch that has become wet because of rain and therefore on which the ball bounces unpredictably. A difficult or unpredictable situation.
Well, there are people outside of the US, some of whom don't even have English as their first language. A quick investigation into this leads me.to believe that there might even be more people outside the US than inside. Most of those people have never heard of a sticky wicket.