On 11 September 2001, I had been in Jerusalem for two weeks, where I was studying at Ohr Somayach through Yeshiva University, where I had studied the previous semester. On the day in question, I had woken up late, although the planes didn't crash into the buildings for another couple of hours. It was actually still during our big lunch break that the planes went into the buildings. Now, although I had spent the previous spring in New York City, I wasn't familiar with what the World Trade Center buildings were (I grew up in central Ohio, after all), so I neither understood their significance nor how many people were there....
There are two other important pieces of the context of my experience of 9/11: the first of these was that there had been numerous bombings - suicide and otherwise - in Israel and we had to be careful about riding buses and going certain places because of Arab bombers. With these planes being led into the towers by Muslim extremists, this wasn't so peculiar, as we were acutely aware of Muslim/Arab terrorism in Israel. You could almost say that Arabs/Muslims wanting to do harm to do Jews and to the West was already on our radar.
The second of these was that, being at Ohr Somayach, we didn't have tvs around - so I never saw the news breaking about the planes hitting the Twin Towers. Moreover, to this day, I still have not seen the footage of the planes hitting the towers. Now, granted, I've seen a brief clip or two of the plumes of smoke emanating from the towers, although I've never seen either the full clips of them being hit, nor have I ever seen any of the coverage. Now, in our day, I'm pretty sure I can easily find coverage of it, but I feel somewhat weird about it, as it would simply be watching an historical event, almost like watching the Hindenburg go down or violence in Rwanda - it's trying to understand a historical event that happened somewhere.
In the immediate aftermath of the attacks on September 11th, we heard (whether rightly or not) that America / President Bush had given essentially a carte blanche to deal with it's Arab terror issue, since America now understood, to some degree, what it's like to deal with terrorism.
Now, having been at yeshivah, we didn't get newspapers nor have any tvs around (although we could go to Internet cafes and catch up on what was going on in the world, check email, etc.), so I wasn't terribly aware of how people back in the US were dealing with the events on 9/11. However, I remember a week or so following the attacks that I was on a bus (yes, I know not the safest activity...) and seeing a newspaper discussing it, but not having seen anything about it at all afterwards.
When I returned Stateside in January 2002, there were two strange things that I noticed: 1) there was a greater sense of nationalism/patriotism in the US, which was not simply strange, but was significantly different than when I had left. When going to another country, I know that things are going to be different than they are in the US, so I don't encounter culture shock. However, when I returned home, I experienced the most significant culture shock of my life: I didn't expect that my own country would be different when I returned(!).
The second thing that was peculiar to me was that the terrorist attacks in September were still in the newspapers(!). Every day, there was something being discussed about the attacks. In Israel, there were attacks, they got covered, and people moved on.
Anyways, I would say that we in yeshivah did not experience the same panic that gripped my fellow America citizens in the US at the time and that being aware of terrorist attacks by Arabs/Muslims was already part of our world. I also imagine that other college students studying abroad at the same time may also not have experienced 9/11 the same way those still Stateside did....