The Fourth of July is about the flag. Thanksgiving is for the family. Today is America's other national day - a beer-drenched,over-hyped festival of sport known as the Super Bowl.
The sport in question is American football, a bone-crushing battle between two teams mostly consisting of 20-stone-plus behemoths. Gridiron, as it is also known, has been described as the perfect metaphor for American life: endless committee huddles punctuated by brief interludes of extreme violence.
This year the contest, the final showpiece match of the National Football League season, takes place in Houston, an ugly, sprawling Texas metropolis which has been preparing for Super Bowl XXXVIII for a year.
In many ways, Super Bowl Sunday resembles an English Cup Final Saturday of old, when the country stopped, rivetted to radios and television. Like our FA Cup Final, it is an occasion less for true devotees than for celebrities, corporate sponsors and VIP guests. Of the 70,000 seats at Reliant Stadium, only a quarter will be occupied by true fans of the Carolina Panthers and the New England Patriots - and the rest by what Roy Keane famously called the prawn-sandwich brigade.
The NFL claims a worldwide TV audience of one billion for what the New York Times says is probably "the biggest one-day sports event in the world". Have they never heard of real football's World Cup Final? But, we are told, 137 million people in the US will watch. By coincidence or otherwise, that is almost exactly the same number of dollars as CBS will rake in from the advertising during the game.
The Super Bowl is also the championship game for the advertising industry. During Super Bowl I, a 30-second spot cost $42,000 (some $240,000 in today's dollars). This time a similar spot will cost an average $2.3m - and the companies aren't skimping on the contents. IBM has Muhammad Ali promoting its Linux operating system. Cadillac is using Hollywood special effects to push its 2004 models. Two erectile dysfunction drugs, Cialis and Levitra, will also be competing (though macho football fans aren't meant to need that kind of assistance).
Sociologists like to measure the tone of the ads (notably sombre in the immediate post-9/11 Super Bowls of 2002 and 2003) as a barometer of the national mood. This year ismuch chirpier. Homer Simpson will be plugging Mastercard, and an elderly couple will do hilarious battle for a packet of Lays potato chips.
Inevitably, in an election year, politics rears its head. The federal government has bought spots for anti-drug and anti-smoking ads, but MoveOn.org, the Democratic activist group, is furious that CBS won't accept an anti-Bush ad. "We'll be seeing ads sponsored by beer and tobacco companies and the White House," says a spokesman, "so why not ours?"