The Picky Eagle

Richard Haass’s book The Picky Eagle: How Democracy and Xenophobia Limited U.S. Territorial Expansion is an excellent book which explains why the United States abandoned territorial expansion and instead built the modern international system which outlawed territorial acquisition.

Spoiler: The U.S. gave up on expansion because it concluded that its neighbors weren’t worth the trouble of annexing and incorporating into the United States. Puerto Rico still isn’t a state.