Megan McArdle, Columnist

Welcome to Trump's America. Start Digging the Moat.

Isolationism like we haven't seen before. Such great isolationism. Just terrific.

America First.

Photographer: Joe Raedle/Getty Images

“America First.”

I expect that’s the line that will get the most mention from Donald Trump’s inaugural speech. He said it twice in a row, to emphasize a new role for America in the world: not the leader of the free world, but an exceptionally large island between the Atlantic and Pacific oceans.