Richard Haass is the president of the Council on Foreign Relations. He is the author, most recently, of "Foreign Policy Begins at Home."

There are many candidates for what constitutes the principal national security threat to the United States. Even an abbreviated list would include the Islamic State and terrorism more broadly, a more assertive China, a revisionist Russia, Iran, North Korea, climate change and an Ebola-like pandemic.

Political disagreements make the U.S. less reliable, leading friends to take matters into their own hands and foes to challenge U.S. policy, thinking they have little to fear.

All these threats should be taken seriously. My choice, though, for what threatens America most is very different: our internal political divisions. The divisions are between the White House and Congress but also within the parties and between citizens and their government. One result is that the United States does not have the resources it needs for national security — and what resources it does make available are often spent to satisfy political rather than strategic needs.

United States infrastructure is woefully inadequate, leaving us less resilient in the face of natural and artificial disasters and less competitive in the face of global competition. Also making this country less competitive is an outmoded immigration policy that does not do enough to allow the most talented people to stay here — and a K-12 education that does not do enough to prepare citizens for the world they are to enter. Meanwhile, nothing is being done to rein in entitlement costs that will soon cause the debt to skyrocket. Standing in the way of needed reform in all these areas are political disagreements.

The result is a country weaker than it should be, failing to set an example others want to emulate. The same divisions make us less reliable, leading friends to take matters into their own hands and foes to challenge us in the belief they have little to fear. Add to this a lack of consensus over U.S. priorities around the globe and you end up with a far more disorderly world because the most powerful country is unable to provide the leadership that no other country can.



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