As a child growing up in the U.S., you are told that St. Patrick is the patron saint of Ireland (true) and that he drove the snakes out of Ireland (false). You are also told that wearing green is the main point of the holiday that bears his name, with failure to do so resulting in you getting pinched.
As you grow up you see the snakes story for the crock it is, and based on your observations (and eventually on your experiences) you come to believe that the main point of St. Patrick's Day is
In many ways, St. Patrick's Day is one oddity of a holiday. It celebrates a genuine Catholic saint, but few of us know anything about him other than the fact that people celebrate him by getting drunk every March 17th... And most of us who celebrate him in the U.S. are not Catholic, instead identifying ourselves as Protestant or even agnostic... And although the holiday is specifically tied to an island with a population smaller than New York City's, it is celebrated around the entire friggin' globe.
Jaded, fortysomething Americans such as myself like to say (while consuming a pint of Murphy's Stout and ordering a round of green Bud Light) that St. Patrick's Day is an American construct gussied up in Irish drag. We like to say that it has no real ties to religion, that it goes unobserved in "the old country," and that it is nothing more than an excuse for our alcoholic countrymen to get falling down drunk and chalk it up as "tradition." But we are wrong -- wrong! -- because the Vatican made it an official holiday way back in the 1600's. Even the gluttony/drunkenness thing has some churchy basis when you consider that on March 17th the Vatican lifts the Lenten restrictions on drinking alcohol and eating.
Perhaps the diaspora of Irish people explains part of St. Patrick's Day's wide appeal, since the sheer size and extent of their dispersal makes the scattering of Jews from the Holy Land seem trifling.
Long ago I remember hearing that there were 4 million people living in Ireland and 44 million Irish people living in the United States... Huge percentages of the populations in Canada's Atlantic provinces, especially Newfoundland and Labrador, are made up of people from Irish stock... An estimated one million people of Irish ancestry reside in Argentina...Ireland accounts for the second largest ancestry group in Australia... etc. etc.
When you consider the outsize influence Ireland's diaspora has had on the world, you really start to appreciate the role Irish genealogy plays in our affairs. We know the Beatles as an English band, but all of them except Ringo trace their ancestry to Ireland, not Liverpool...Oscar Wilde made his mark as London's biggest playwright, but was born in Dublin...John Wayne came from Irish stock and so did Maureen O'Hara, the smoking-hot redhead who often starred alongside him and is still alive and kicking at the age of 93.
In the decisive decade of the Cold War, America's president was Ronald Reagan and Canada's prime minister was Brian Mulroney. Both were Irish by blood, and together they helped hasten the end of the Soviet Union. In the following decade, Irish-by-blood Tony Blair became the most influential British Prime Minister of the post-Thatcher era.
In the sports world, seemingly white-as-can-be boxing champ Jack Dempsey was an American of Irish descent -- and so was seemingly black-as-can-be boxing champ Muhammad Ali, whose great-grandfather was born in County Clare, on Ireland's west coast, before moving to America.
Still, genealogy and diaspora can't completely explain the global reach of St. Patrick's Day. Not when Japan (yes, Japan!) celebrates it not just on March 17th but all month long. Not when Russia's notoriously xenophobic government plays a part in staging an annual St. Patrick's Day parade in Moscow. And not when prickly French Montreal also hosts a parade.
Some things just can't be explained. And it's often better that way.