Is diversity a root cause of dual loyalty?
"We can't be divided by race, religion, by tribe. We're defined by those enduring principles in the Constitution, even though we don't necessarily all know them."
So Joe Biden told the firefighters union this week.
But does Joe really believe that? Or does that not sound more like a plea, a wistful hope, rather than a deep conviction?
For Biden surely had in mind the debate that exploded last week in the House Democratic caucus on how to punish Somali-American and Muslim Congresswoman Ilhan Omar for raising the specter of dual loyalty.
Rebutting accusations of anti-Semitism lodged against her, Omar had fired back: "I want to talk about the political influence in this country that says it is OK to push for allegiance to a foreign country."
Omar was talking about Israel.
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Republicans raged that Nancy Pelosi's caucus must denounce Omar for anti-Semitism. Journalists described the raising of the "dual loyalty" charge as a unique and awful moment, and perhaps a harbinger of things to come.
Yet, allegations of dual loyalty against ethnic groups, even from statesmen, have a long history in American politics.
In 1915, ex-President Theodore Roosevelt, at a convention of the Catholic Knights of Columbus, bellowed: "There is no room in this country for hyphenated Americanism ... German-Americans, Irish-Americans, English-Americans, Scandinavian-Americans, or Italian-Americans.
"There is no such thing as a hyphenated American who is a good American. The only man who is a good American is a man who is an American and nothing else."