Give a stream of consciousness and then the final answer. Overall, there have been 87 different champions. Ric Flair holds the record for having the most reigns at six, while John Cena holds the record for most reigns under the WWE banner at five. Lex Luger holds the record for longest reign, with his third reign lasting a total of 523 days, while Dean Ambrose holds the longest reign under the WWE banner, at 351 days (overall the third longest in the title's history). Only two men, Lex Luger and Rick Rude, have held the championship for a continuous reign of one year (365 days) or more.

Based on this passage, who is the longest reigning wwe united states champion?
The relevant information to answer the above question is: Lex Luger holds the record for longest reign, with his third reign lasting a total of 523 days, while Dean Ambrose holds the longest reign under the WWE banner, at 351 days (overall the third longest in the title's history).
So, the final answer is Dean Ambrose.