It's like this:Frankster said:snip
The US has no football cred. To beat them is to be expected, to lose against them would be shameful.
England is a WC champ and has a good team. Losing to them carries no shame, winning against them is superb.
Italy is also a WC champ and has a very good team. Costa Rica is neither, so beating them is doubly celebrated.
Then there's your perception of football as "just football". To most, if not all, underdeveloped third world countries football is their only means of pride and self-worth, and big tournaments like the World Cup carry an enormous hype and prestige that transcends individual interest on the sport itself. For many of these countries it's also their one chance to go elbow to elbow with the first world elite and shine against it on some sort of layer. All of Latin America - this isn't an exaggeration - will pine for the sudaca underdog going against a country like England, Italy, Spain, Germany and the Netherlands because of this, bar the usual neighborly conflict (like Argentina-Uruguay).
Winning the FIFA WC doesn't change anything most of the time, but it means a lot to these people.