Halloween is not a a celebration that American would have created on their own. It originated with the pagan Druid priests before the Roman era. The Catholic Church later tried to Christianize into All Saints Day, but it didn’t last.
I wouldn't say it didn't last. All Saints Day is still observed by 1.3 billion Catholics around the world. The modern day version of Hallowe'en is more an English-American phenomena, popularized in modern times by those who profit monetarily by it (candy, costumes, decorations, alcohol, etc.). Back when I was a kid in the 1960's it was fairly innocent, but now, as someone here mentioned, it has been turned into an excuse for adults to get drunk and celebrate gore and evil. Most other countries in the world don't celebrate it, and that is why El Salvador is wisely trying to get rid of it. It never was part of their own culture.
Well if you see it (correctly, in my opinion) as Catholic folk practices for All Saints that got outlawed in England, driven underground, and then eventually secularized, it’s very easy to see how Americans created the modern version of the holiday.
The exact same thing happened with Christmas, Mardi Gras, Easter, St. Patrick’s Day, and Thanksgiving. America has a funny way of completely taking religion out of religious holidays.
Halloween was completely unknown in Italy until quite recently—even though they always celebrated All Saints Day.