Rusev
Rusev just becomes a monstrous heel if the United States championship is around his waist. He has been a dominant champion before and can add to the US championship legacy if booked properly, again. Jericho will have to turn babyface for the feud, of course. But, just imagine the achievement he will pull off before Jericho put him over before leaving after Wrestlemania. The Bulgarian Brute could brag about it for the entire year going forward to take on more names like Rollins, Zayn or Cass, defending the title.