How can the most powerful militaries on the globe with all their sophisticated spying networks, intel, and sheer might not be able to halt terrorism and those who support terrorism. HOW?

The answer to this is simple. The U.S. military is not all that impressive except on paper, and intelligence agencies aren't omnipotent or unified. It relies too much on the appearance of effectiveness vs. actual effectiveness. Relying on technological advances at the expense of their strategic and tactical abilities, the advantage of overwhelming economics, and a genuinely aimless government with no actual goals, the U.S. military is made impotent by political malaise and a lack of any real wartime experience. They don't know the art of war, they know the art of occupation, the art of marketing, and the art of point-and-click drone "combat".

Korea beat them, Vietnam beat them, Cuba beat them, Afghanistan beat them, and Iraq could have beat them too if they hadn't let the U.S. military lazily assemble on its doorstep for six months unchallenged.

Then there's also the politics. The Pentagon and the CIA are fighting eachother in Syria. There's a lot of drug money to be made.

I guess it all comes down to money. They think they can buy an army that wins, just the same as they think they can "free market" a nation into prosperity and democracy, just the same as some government bureaucracies just see dollar signs attached to regional instability.

Do not attribute to malice that which can be attributed to the degrading effects of Market ideology and general arrogance.