#4 Jinder Mahal
Some might not see the point in this matchup after Jinder Mahal lost his WWE Championship to AJ Styles in Manchester, but it could still work if WWE were to insert The United States title into the feud. In fact, the inclusion of The United States title makes the match WrestleMania worthy in a way.
Of course, WWE could probably do this at any one of their pay per views and have it be a huge success, especially since The WWE Universe would be forced to pick sides between Cena and Mahal, but holding this one off for one of the big four pay per views might be the best idea here.
With that being said, the matchup would also be a great way to utilize Mahal as an anti-American heel and make the moment when someone unhands the belt from him even sweeter than usual. Sure, having Cena be the one to do that isn't ideal for everyone, but fans can't deny that it would create a huge pop if it does happen.
In the end, Mahal beating Cena would be a great way to get some of Mahal's heat back after falling out of the title picture and would also give him another run with one of the company's top titles. Finally, it would make Jinder Mahal's time with the title must-see TV, especially since Mahal would be spewing anti-American sentiment to get massive heat from fans.