Over the years, Bruce Springsteen and John Mellencamp have followed roughly similar career arcs. They both debuted in the ’70s and under-appreciated singer-songwriters. They both became stadium-status MTV icons in the ’80s by singing anthemic and synthy rock anthems about common-man struggles. They have both since eased into elder-statesman respectability. Springsteen and Mellencamp aren’t exactly on equal levels historically, but it’s fair to call them peers. And now they have a song together.