Marine General Joseph Dunford testified to the Senate Armed Services Committee in his confirmation hearings to become Chairman of the Joint Chiefs of Staff. He looks to me like someone who understands the world. When asked what the greatest threat to the United States was, he said it was Russia. Followed by China and North Korea. Of these three, only Russia is actively making dangerous moves.
I am especially heartened that he did not say ISIS or al Qaeda in answer to that question.
It seems to me that the bloodthirsty fundamentalist extremist segment of the Muslim world can harm us, and is certainly trying. But they really don't represent an existential threat to this country. They are a terrorist threat, which is quite different. They could blow up another building, they could kill hundreds of Americans and Westerners, they could shock our sensibilities with horrific atrocities, they can do all that they can imagine to do to promote deep and disgusting depravities of violence. But they aren't an existential threat to our country.
I believe their intent is to act so atrociously as to bait the United States into making the same mistake that W made - send ground troops into the Middle East and wage war against - Muslims (which side to we pick in this horrible civil and religious war, and why?) This would frame the fanatic jihadists barbarities as Islam against the crusading U.S. This would be an amazingly stupid mistake for us to make. It would be a tremendous aid to the recruitment of Muslims to the barbarous jihadist side. It would grow the threat rather than reduce it, or so it seems to me.
I don't believe Russia is out to destroy the U.S. but it does have enough nukes to do so, so they actually could be an existential threat. And good for four star General Dunford for seeing that and being willing to take that threat seriously.
Protect ourselves against terrorism, don't get sucked into their pathetic civil wars.