Which enemy of America should be the biggest concern?

All of these countries pose a security threat to us. They are all different but all threats. A few have already talked about the real risk to America. America was an ideal, a vision for freedom and liberty enshrined in our founding documents.

We have a issues of the heart, of the mind and of the spirit that are far more threatening to us than these countries. We have become complacent, under educated, to dependent, to politically correct, to cult of personality driven and many other things that are eroding the foundation. As Ben Franklin was asked when leaving the Constitutional Convention "Well, Doctor, what have we got, a republic or a monarchy?"With no hesitation whatsoever, Franklin responded,"A republic, if you can keep it." He knew the work of keeping it would be far harder than anyone would think and he was right.

There are no guarantees. We have been insulated for so long we have forgotten what it has taken to get here and that is as sure a sign of trouble as anything.

Islamic Radicals

The ones who want to destroy us

None of those are the biggest concerns at this time, but all need watching. Currently, IMHO, the greatest current threat to our Constitutional Republic is the corruption of corporate media and next is the state of our Nation's education and historical illiteracy of the majority of our Nation.

I share CPT Jack Durish sentiment on this issue...none of the above!, the enemy within is the most dangerous today

I aslo believe Americas greatest threat is 1.itself and 2.ISIS

None of those, the big enemy is economic decline. If we continue to decline we will at some point be unable to address any of these threats. The middle class continues to shrink and good jobs are still being replaced by poorly paying jobs.

None of the above, fracking ignorance of the American public will be our own worst enemy.

The domestic ones that attack from within at high political offices

None of the above. Our greatest enemy lies within our borders. The enemy is those who wish to continually divide us and keep us weak.