Metonymy Gone Bad

metonymy: n. Rhet. the use of the name of one object or concept for that of another to which it is related, or of which it is a part, as "scepter" for "sovereignty." [The Random House College Dictionary]

[from the movie "Canadian Bacon" (1995)]
Boomer: The capital Toronto.
RCMP Officer at Headquarters: No, the capital of Canada is Ottawa.
Boomer: Yeah, right. Do we look that stupid? Ottawa!
Roy Boy: Nice try, Dudley.

This is a gaff that, were any layman to make it, would be perhaps funny, but it's not exactly super-common knowledge. Robert Kagan, however, is a world affairs columnist for the Washington Post. He really should know better. Kagan writes:

In East Asia, meanwhile, U.S. relations with Japan grow ever closer as the Japanese become increasingly concerned about China and a nuclear-armed North Korea. China's (and Malaysia's) attempt to exclude Australia from a prominent regional role at the recent East Asian summit has reinforced Sydney's desire for closer ties.

As Matt Yglesias snarkily comments, "But what do they think in Canberra?"

Canberra, not Sydney, is the capital of Australia.