Tell that to Chomsky.
Gladly, given he's not exactly an expert on the subject.
I think that the reason people tend to focus more on Islam is that these other places you mention don't tend to produce suicidal maniacs that are a threat for the rest of the world.
That's neither here nor there, really. Radical Islamism is a violent political ideology loosely related to Islam, in the same way that the Christian Identity movement is a violent political ideology loosely related to Christianity. Regressively boiling down discussion to whose got the biggest body count rather misses the point; if you're going to do thst, you might as well declare war on drunk drivers and wasps.
it is also increasingly more relevant given the frequency of these attacks.
This is not quite true. In France, where we've seen the majority of recent incidents, the frequency violence being perpetrated still doesn't come close to that perpetrated by Islamist groups seeking to strike back at the imperial powers fighting popular resistance in Algeria. More generally, this isn't close to the level of violence perpetrated across wider Europe by Marxist-Leninist urban guerrillas or by right-wing parallel state organisations set up by Gladio. Or for that matter Irish Republicanism and the overspill of that sectarian conflict.
In the cases of Belgium and France it is rather a case of chickens coming home to roost. Both have a sordid history with North African descended citizens and migrants; rounding them into effective ghettos, institutionalised discrimination, grinding poverty, police harassment. Given their social and economic circumstances the high levels of radicalisation are far from surprising.
As an aside, don't even get me started on Switzerland. They didn't even have women's suffrage until 1991. People talk about sexist policies in the Islamic world...
Widespread outrage among Muslims regarding religious cartoons or parodies is also disproportionate.
It's disproportionate from a Western cultural perspective, but entirely expected to anyone whose actually spent time studying Islamic culture. The absence of any Islamic enlightenment, which is at least partially down to historical imperialism, plays a significant part in this, as does the relative poverty of most Muslim majority countries. It's no coincidence that the wealthiest and economically liberal Muslim states don't seem to be exporters or sufferers of these problems to anything like the degrees that poorer, economically authoritarian ones are.
So what do we call it when a state's military deliberately and knowingly attack non-military targets?
A war crime? Technically, that's what it is. Terrorism cannot be a war crime as terrorists are not bound by the laws of war, due to not being states.