By the late nineteenth century, no combination of countries in the Western Hemisphere could meaningfully threaten America’s security. The one European power—Britain—that might have challenged the United States in its own backyard was menaced by Germany and chose to appease the Americans instead.9 The United States was the sole great power in its hemisphere, which allowed it to project that power around the world. America could build an ocean-going navy rather than heavily fortifying its frontiers. It could enter the world wars of the twentieth century late and allow countries in Europe and
...more

