"Только силой с этим явлением [terrorism] не справиться, тем более, что смерть террористов не пугает".
I was intrigued at the usage of the infinitive справиться here. Normally the third person plural is used in order to express an impersonal subject (like "говорят..." in the sense of "it is told that...").
But, apparently, "не справиться" translates here as "one can't cope with"?
Не справиться here can be thought of as a short form for не(-льзя/-возможно) справиться. So yes, your translation is correct while a more literal one would sound like 'it's impossible to cope with (to overwhelm/overcome)...'
No, it's not an idiom, it's one of grammatical vehicles to express inability, constructed as
Dative + negated (perfective) infinitive
In positive statements, which express ability, either the inflected modal verb мочь is employed or the inflected adjective способен
Compare:
Мне не поднять этот камень VS Я могу/способен поднять этот камень
A positive expression of ability similar to that of inability requires for example addition of adverbial phrases под силу; по плечу if it's about physical or intellectual ability or по средствам; по карману if it's about financial ability
Мне не поднять этот камень VS Мне под силу поднять этот камень
However their use is context dependent.
