america putting its thumb on the scale is what creates an even easier environment for instability. Without the US acting as the schoolyard bully's bigger brother who is 4 grades ahead israel and Iran would be more moderate.
Hell if it wasn't for the US intervening at israel's behest in Iraq, Iran would be more contained to begin with.
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Islamic fundamentalists can't conquer their own turf even if you removed israel. Most spreading of truly insane muslim terrorism has been enabled by US actions, funding the Mujahedeen in Afghanistan which tied into later Egyptian terror cells and Al'Qaeda, the US giving material aid to ISIS in Syria, Knocking Libya out of stability and much much more. None of it was accomplished by the feats of fundamentalist Islam itself but foreign influence using them as tools to work for their interests.