The National Interest explains how U.S. alliances should be judged:
The United States stands at the center of a far flung global alliance system, which commits it to defend the security of countries rich and poor, great and small, liberal and illiberal. The principal U.S. formal alliances are the North Atlantic Treaty Organization, the U.S.-Japan security treaty, the Republic of Korea Treaty, and the Australia-New Zealand (ANZUS) treaty. The United States has less formal relationships with Israel and several Arab states, and many others around the world. The foreign-policy establishment insists that all of these alliances are central to our security. …
The value of U.S. alliances should be judged on their contribution to U.S. security—the ability to defend the safety, sovereignty, and territorial integrity of the United States. …
Supporters of the present alliance system routinely minimize its military costs. The Department of Defense’s accounting systems make the calculation of such costs difficult. …
These alliance commitments create a special kind of “moral hazard.” The extravagant insurance that we offer these countries encourages them to engage in risky behavior. For the Europeans and Japanese, this consists of buying too little military insurance for themselves. Their defense budgets are too small even to sustain their present force structures.
