The attacks of 9/11 were intended to punish America for its foreign policy and its treatment of certain religions. Whilst the attacks attracted certain people to the religion as they agreed with the aims of the attack, it also turned at least as many people away from Muslims and other similar groups. That's an effect in itself, along with the other effects that that the attack led to. As the events may have galvanized Muslims towards their faith, it will also galvanize that were unsure about the faith into hating them for the attacks. This will lead to an almost underground following of your faith for worry about attacks on yourself or where you follow your religion. It became like the Christians in ancient Rome for a period, where they had to hide in order to practice their religion for fear of persecution.
Certainly since the attack, the persecution will have lessened to a point but the war in Iraq and Afghanistan have fueled the discourse in another way. The Muslims feel more fired up as they hear about the problems in their homeland and see the local soldiers going off to war. The soldiers will want to support their country and their fellow soldiers, they will be fighting in an area where their Muslim neighbours may have family and friends. Indeed, they could conceivably know people that have lost lives linked to people they know or who are local to them. There will be people and groups of people in virtually every town or state that won't communicate with other groups due to the war, the war in turn will fire up memories of 9/11.
To confuse things further, there will be many people of no religion or a different religion who don't support the war for other reasons. This makes three differing groups, all who will be making their points vocally and all who will find another group to argue with. Also, there will people who wish to make their points in other ways, certain groups may be banned from shops for example. A pro-war supporter may have arguments within their own families to mix things up further.
If you decide you need a faith to follow or one to change to the modern world means you have to look further then just which deity is followed and how. You have to consider what your religion represents or appears to others to represent. If you say "Muslim" to some people, they will think of violence and persecution of women; although this is only true in a minority of cases, it's a view some will have. You will find that most cities and towns will have a certain amount of families who have lost members from the terrorist attacks and from the wars since, they may be the ones with the narrow views. Similarly, the narrow views have led to some joining the Muslim faith because of the attacks and in order to commit more attacks. Indeed, some of the terrorist attacks over recent years in the Muslim name have been committed by those who weren't Muslim at the time of 9/11.
Those who were Muslim and didn't agree with the attacks don't appear to have changed faith since the attacks, they have stayed true and decried the attacks and the terrorists. They have often worked from the inside to try and stop people joining to be terrorists, or those already in the faith doing similar. All faiths need to do more to attract people to them but will also to be careful how they are perceived by the world at large. They need to concentrate on how they follow their faiths, but must be aware of factions and groups within their remit. It takes only a small group to tarnish millions, but the majority can in most cases can control and smother the bad seeds. At the moment, if you say "Osama bin Laden," many will think of a Muslim terrorist; he is a minority influencing a slightly larger minority, one that the majority could silence if they wished.