Nothing shuts down a person's higher reasoning functions quite as fast as the word "tradition." If it was good enough for our ancestors, it must be good enough for us, damn it!
Unfortunately, some of the most "ancient traditions" still followed today come from people who knew this, and just made them up off the top of their head.
According to this ridiculously schmaltzy video, this video with a hilariously ironic choice of music and 90% of the people in states beginning with the letter A, the pledge is an inviolable American tradition. Given the massive hissy-fit that erupts any time someone tries to change a single word, you'd think the version you grew up reciting was written into the constitution after the Founding Fathers watched a giant bald eagle fuck every letter into Plymouth rock.
An image that would bring a tear to Captain America's eye.
How Old It Actually Is:
The idea of pledging allegiance to the flag was basically an early viral marketing gimmick. It was first published in 1892 in a wildly popular children's magazine named The Youth's Companion. The much-bitched-about "under God" was only added to the pledge in 1954.
Who Made It Up:
Daniel Ford, the man who ran The Youth's Companion, dreamed of putting an American flag in every classroom in the country.
The man loved him some America.
Within a year, 30,000 flags had been sold. Our calculators tell us that comes out to $300,000, which was a lot more impressive a sum in 1892. The man who actually wrote the pledge was a former minister named Francis Bellamy. He was a Socialist (aka, a dirty commie) whose stated mission was to create in America's youth a habit of automatic reverence and utter loyalty to the country. He even came up with an original salute for children to give while reciting the pledge...
Things got awkward around '41.
The decision to add "under God" was made at the height of America's brief flirtation with paranoid schizophrenia, otherwise known as McCarthyism. Congress felt the pledge, like most people at the time, just wasn't American enough. How were these children standing around the American flag, pledging "allegiance to the flag of the United States of America, and to the republic for which it stands" to know that they weren't in the Godless Soviet Union? Thus, Congress added God to the pledge, and every generation who passed through a public school after 1954 was transferred into a flawless vessel of patriotism.