The appointment of British editors like Will Lewis at the Washington Post and Mark Thompson at CNN raises questions about their impact on reviving struggling U.S. mainstream media.

In a relatively short period, the crisis in American news media has brought about an unanticipated outcome: the invasion of executive news suites by British editors, who, according to analysts, bring a "killer instinct" to news gathering and significantly lower the diversity quotient in news leadership.

Bri...