#1 Roman Reigns
The reason why WWE fans hated Roman Reigns (before his departure last year) is the same reason that could help the United States Championship to get the center stage: He takes all the spotlight!
The main problem with the title currently is that none of the recent champions have been booked properly and given the proper TV time that they deserve as the champ.
A champion is someone who leads the division, whom others can look up to as a motivation to do better. But the current situation with the US Championship is very different.
Putting the title on someone like Roman Reigns would ensure that the storylines for the title are booked properly. Roman as the United States champion could get the title all the attention that it needs. The title would again start meaning a "championship" rather than just a "belt".
Having Roman feud against another top main-event player for the US title would be best for the business.
Let us know how you feel about the current status of the championship and how it can be improved!