Today is Cinco de Mayo, which while an important holiday in Mexico is not nearly as big a deal as it is here north of the border where it's a good excuse to get drunk on tequila.
Most of the folks getting drunk think they are celebrating Mexican independence day but that was actually September 16, 1810. What Cinco de Mayo actually celebrates is the Battle of Puebla on May 5, 1862.
Without getting bogged down in the details, while the United States was busy with its Civil War, Napoleon III of France thought it would be a good idea to turn Mexico into a French client state and so invaded it. The Battle of Puebla was the first victory of the Mexicans over the French.
So really you have to ask yourself, what's the big deal. The Mexicans beat the French. Everyone beats the French. If we had a party at every French defeat we'd all be perpetually either drunk or hungover.
Snark aside, the Puebla is in fact something for Mexicans to be proud of. It's not every day that 4,500 militia men can defeat a larger (6,500 man) army of crack regulars. My point is though, if you are going to use a foreign holiday as an excuse to party at least know why you are partying.