I was an immigrant of several years when 9/11 happened. It changed me in that I realized that day that I belong here. This event had happened to my country, and there was no denying that.
One thing I did experience was that everyone around me had all of a sudden come down to my level. Everyone's emotions were suddenly at my level.
About two weeks later, though, I saw most folks drifting back up to the level where they used to be, some 200 feet above me. Of course, I was not aware that others had been drifting far above me until that moment.
My European background with all those wars going on all the time had pushed me and my original culture down to that 200 feet level below that of those in societies that were never hurt by (many) wars at the home front.
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In my old country, there is a Bible belt. It is exactly where the war of independence with Spain was the worst.
The USA appears to have a Bible Belt too, exactly where the civil war had been the worst. Trauma of the past reverberates to the present.
Did 9/11 change us? It changed me. It changed society around me that subsequently tried to veer back into its original state.
But we are not veering back the way we were. Not possible. We did get damaged. We did get pushed a little bit lower from where we were before. But... we did veer back to a large extent. Partly, because that is in our culture. Partly, because the damage was contained to one day and did not last for years on the home front.