“Uneasy lies the head that wears a crown,” Henry IV lamented, per Shakespeare. The same can be said, lately of “King Dollar.” That moniker is a shorthand for the greenback’s role as the world’s leading reserve currency. Yet President Trump’s tariffs are sparking a new wave of doubts over the dollar’s reign. “The mighty dollar,” Marketwatch warns, “is falling apart,” stirring echoes of the “Nixon shock” in 1971 when America left the gold exchange standard.