Early in this century, the humorist Stephen Leacock said the American innocent must prove his folksy virtue by being semi-inarticulate, mouthing things like "Heck, b'gosh, b'gum, yuck, yuck." That is why Jimmy Stewart's hesitating-gulpy delivery was reassuring. His appeal went so deep because it touched America's belief in its own simplicity. When Mark Twain wanted to present himself as a traveling American, he called his tourist book The Innocents Abroad.
America is the New World. What it has to offer the jaded Old World is its fresh eye and unspoiled candor. When Stewart goes to Washington as Mr. Smith, a band...