Jonathan Zimmerman is a professor of history and education at New York University. He is the author of “Small Wonder: The Little Red Schoolhouse in History and Memory” (Yale University Press).

I just returned from a quick trip to Great Britain, which once ruled a fifth of the world’s inhabitants and a quarter of its land mass. But then the British instituted a system of social welfare, including national health care, which diminished their strength and confidence – and paved the way for the dissolution of their empire.

So said presidential hopeful Rick Santorum earlier this month in Iowa, where he ran a close second to Mitt Romney in the Republican caucuses. Critics quickly seized on Mr. Santorum’s confused chronology, noting that the British left India – the jewel of their empire – in 1947, and their National Health Service wasn’t established until 1948.

Yet when I recounted Santorum’s remark to a colleague in England, he had a very different response: “Why does the guy like empire so much?”

The answer isn’t hard to find. Like most of the other GOP candidates, Santorum seems to see America as the rightful heir to British global domination. All we need is a firm belief in our own superiority, which the British allegedly forsook after World War II....

[M]y colleague in England, who happens to be Irish ... wryly pointed out [that] nobody in Ireland – which suffered three centuries of vicious British rule – would ever put in a good word for imperialism.

Neither should we. If we really want to be an “exceptional” world power, we should resist the idea of empire wherever it arises. Despite what you hear from Rick Santorum, health care didn’t bankrupt the British Empire. In all the ways that matter, it was bankrupt from the start.