Germany, which had a 2-1 win over Australia earlier in the week, took a 1-0 lead against the Americans when Sabine Lisicki recovered to beat Meghann Shaughnessy 4-6, 6-0, 6-4 in the women's singles.
Blake's win means the round robin Group A match in the international mixed team tournament will be decided by the mixed doubles.
The United States needs to beat Germany and Australia to have any chance of reaching the final after losing 3-0 to Slovakia in its opening match.
Blake converted only one of 18 breakpoint chances - in the opening game of the thirst set - but that was one better than Kiefer.
Russia was to play Taiwan in Group B in the night match.
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Slovakia beats United States at Hopman Cup
France takes 1-0 lead at Hopman Cup
