From the stony streets of Boston to the rail lines of California, from General Relativity to Google, one of the surest truths of our history is the fact that America has been built by immigrants. The phrase itself has become a steadfast campaign line, a motto of optimism and good will, and indeed it is the rallying cry for progressives today who fight against tightening our borders. This is all well and good, Philip Cafaro thinks, for the America...