A similar problem presented itself during the Cold War. In this case, the United States did not trust the European balance of power to contain the Soviet Union. That balance of power had failed twice, leading to alliances that brought the United States into the affairs of others. The United States calculated that early entanglements were less risky than later entanglements. This calculation seemed to violate the Jeffersonian principle, but in fact, as with Louisiana, it was prudent action within the framework of the Jeffersonian principle.
NATO appeared to some to be a violation of the founders' view of a prudent foreign policy. I think this misinterprets the meaning of Jefferson's and Washington's statements. Avoiding entanglements and alliances is a principle worth considering, but not to the point of allowing it to threaten the national interest. Jefferson undertook the complex and dangerous purchase of Louisiana because he thought it carried less risk than allowing the territory to remain in European hands.
His successors stumbled into war partly over the purchase, but Jefferson was prepared to make prudent judgments. In the same way, Woodrow Wilson, Franklin Roosevelt and Harry Truman, realizing that avoiding foreign entanglements was impossible, tried to reduce future risk.
Louisiana, the two world wars and the Cold War shared one thing: the risks were great enough to warrant entanglement. All three could have ended in disaster for the United States. The idea that the oceans would protect the United States was illusory. If one European power dominated all of Europe, its ability to build fleets would be extraordinary. Perhaps the United States could have matched it; perhaps not. The dangers outweighed the benefits of blindly adhering to a principle.
A General Role
There is not an existential threat to the United States today. The major threat is militant Islamism, but as frightening as it is, it cannot destroy the United States. It can kill large numbers of Americans. Here the Jeffersonian principle becomes more important. There are those who say that if the United States had not supported Israel in the West Bank or India in Kashmir, then militant Islamism would have never been a threat. In other words, if we now, if not in the past, avoided foreign entanglements, then there would be no threat to the United States, and Jefferson's principles would now require disentanglement.
In my opinion the Islamist threat does not arise from any particular relationship the United States has had, nor does it arise from the celebration of the Islamic principles that Islamists hold. Rather, it arises from the general role of the United States as the leading Western country. The idea that the United States could avoid hostility by changing its policies fails to understand that like the dangers in 1800, the threat arises independent of U.S. action.
But militant Islamism does not threaten the United States existentially. Therefore, the issue is how to apply the Jeffersonian principle in this context. In my opinion, the careful application of his principle, considering all the risks and rewards, would tell us the following: It is impossible to completely defeat militant Islamists militarily, but it is possible to mitigate the threat they pose. The process of mitigation carries with it its own risks, particularly as the United States carries out operations that don't destroy militant Islamists but do weaken the geopolitical architecture of the Muslim world -- which is against the interests of the United States. Caution should be exercised that the entanglement doesn't carry risks greater than the reward.
Jefferson was always looking at the main threat. Securing sea-lanes and securing the interior river systems was of overwhelming importance. Other things could be ignored. But the real challenge of the United States is defining the emerging threat and dealing with it decisively. How much misery could have been avoided if Hitler had been destroyed in 1936? Who knew how much misery Hitler would cause in 1936? These thoughts are clear only in hindsight.
Still, the principle is the same. Jefferson wanted to avoid foreign entanglements except in cases where there was substantial benefit to American national interests. He was prepared to apply his principle differently then. The notion of avoiding foreign entanglements must therefore be seen as a principle that, like all well-developed principles, is far more complex than it appears. Foreign entanglements must be avoided when the ends are trivial or unattainable. But when we can get Louisiana, the principle of avoidance dictates involvement.
As in domestic matters, ideology is easy. Principles are difficult. They can be stated succinctly, but they must be applied with all due sophistication.
