If you're unfamiliar, this gigantic because of the numbers: Djokovic is one of the most dominant players in tennis history and had won the last FOUR Grand Slams. In 27 Majors, he's never lost in the 3rd round. He's by far and away the #1 player in the world and came into Wimbledon on a 30-match winning streak. Querrey, on the other hand, is a solid player but he's never cracked the top 10 and certainly has never won a Major. He has some singles titles but as the 29 seed in this competition, and with an 0-9 record against #1 seeds in majors, nobody gave him any chance to beat Novak.
Also, American men haven't done much of anything in this sport since the days of Sampras, Agassi and Roddick, and the last time an American ousted a #1 seed at Wimbledon was way back in 2002 (Agassi over Hewitt). So, congrats to Sam! :) And on July 4th weekend, too.