It's easy to understand why countries like Russia, China and Iran would want to rewire the Internet, cutting off access to their citizens and undermining the idea of a World Wide Web. What's more surprising is that U.S. diplomats are letting authoritarian regimes hijack an obscure U.N. agency to undermine how the Internet works, including for Americans.

The failure by U.S. negotiators to stop attacks on the Internet became known only through documents leaked last week. They concern a U.N. agency known...