Chilled it's a bit of a difficult situation intervening in other countries affairs but sometimes the US can even be criticised for not intervening. Intervention was seen as coming too late in Bosnia and there was the feeling that many more could have been saved if it had come earlier. In Syria the intervention was a little more difficult and and add to that we also have the Russians intervening on Assad's side and probably bombing MSF hospitals etc. They have also suffered revenge attacks. I personally don't hate America or Americans as such because I am intelligent enough to know that by no means every American agrees with the actions of whatever government might be in at the time. Just like across the world many people do not agree with the actions or political stance of their governments.
The Islamic aspect is a factor in the sense that many young people from that community who live and have grown up in the west may feel at any time at odds with their traditional background and some of the normal activities western teenagers take for granted, for example wearing what they like, going out with whom they like and to what activities they like. I think what most of us don't realise is that religion for many Muslims is something that governs them in many aspects of their lives, from what they wear, to what they eat, where they go and with whom, who they can marry and in the daily act of worship. It's far more pervasive than many other faiths. I see it around my area many of the teenage Muslim boys go through a phase where they try to be gangsta etc, this tends to be speedily followed by marriage in their early 20's and children pretty quickly afterwards, the girls have a bit less freedom. Some of the boys do go entirely off the rails and end up in the justice system for a variety of offences as well, which can be due to family breakdown which is becoming more common in this community too.
My point is that there is conflict in many young people's minds between the community they come from which holds traditional and often conservative values and the larger evironment they find themselves in.
There is unfortunately a great deal of animosity still towards LGBT community from various quarters. I read of a coach driver in Scotland who recently refused entry on a coach to a young gay couple, telling them people 'like them' should not be allowed on McGill's coaches. I know gay people face this sort of discrimination and lower level all the time.
Easy access to weapons? Well as we all saw this week it seems if you wish to get hold of a weapon to carry out an offence there are ways and means. This man had a responsible job as a security guard, they had investigated him for the remarks he had made but at that point had no real evidence, on paper the gun shop would have not seem him as a risk, after all you cannot deny someone something because of their background. As I've said upthread it is the US which needs to decide how their gun laws should be tightened. Personally I think that the right to bear arms should be by no means universal, but even were that to be so I do think it doesn't exclude the possibility of a determined offender being able to get hold of a gun.