I agree about not "underestimating" them. That should be the case, regardless of who the enemy is.
BUT, they are clearly not as formidable as other enemies we have fought in the past (USSR, Nazi Germany, Imperial Japan), nor are they as formidable as enemies we are likely to fight in the future (China perhaps)
Let face it, what technological advances have the Islamic countries made over the last 100 years? Everything they have is either stolen from us or the Soviets (who stole most of their stuff from us). I guess they "invented" the number zero a few centuries ago, and that has been their "claim to fame". Big deal. Beavis and Butthead could have invented the number "zero"
About the only time they've been able to succeed is when our stupidity exceeded their own (i.e., letting terrorists walk into our country, and banning CCW's and most LEO's from carrying on planes)
Hell, they're still ticked off over the Crusades, and that was nearly a THOUSAND YEARS AGO!!
(I sincerely believe the only thing they'll miss from Western Civilization is air conditioning.)
Really? NEVER underestimate the amount of damage a determined enemy can do with what's on hand.