I wouldn't bother too much about knowing the difference, but its good to bear in mind that one of the most prized competitions is the domestic league title. About the cups, once you start watching you'll learn about them and it'll make more sense.
Do you like Cristiano Ronaldo? and Kaka?
You should have no problem catching games with English commentary on American channels because they GolTV and ESPN air most of the games from many of the top European Leagues. For you information, the top three leagues in Europe are the English Premier League, Spanish Primera Liga (often referred to as "La Liga"), and the Italian Calcio (referred to as the Serie A). The next tier in league rankings is German Bundesliga, Dutch Eredivisie and French Ligue 1. If you want to watch European football (which most of us discuss here) then I suggest you watch more of the Spanish, English or Italian leagues
it can't be helped I guess... money talks