Unable to qualify out of the red group into the championship round, USA's miserable tournament continued when Andy Roddick lost 7-5 7-6(4) to Go Soeda.
However, Ryan Harrison registered the American team's first win when he beat Tatsuma Ito 6-2 7-6(5), and then paired up with James Blake to win their doubles rubber against Ito and Bumpei Sato 4-6 6-0 10-3.
Japan have now lost all three of their ties at the Rochusclub.
Czech Republic and 2011 runners-up Argentina are the only two teams who can top the red group, and their tie kicked off with a 6-1 6-7(2) 6-3 win for Tomas Berdych over Carlos Berlocq.
Defending champions Germany lost their first rubber against Serbia in the blue group as Viktor Troicki defeated German Florian Mayer 7-6(8) 6-3. The winner of that tie will top the group.
Croatia and Russia are playing for pride in their blue-group tie, which began with Croat Ivan Dodig beating Russian Igor Kunitsyn 7-6(0) 6-4.