The United States became the first team in its group to win twice as it marches to a spot in the quarterfinals.
The 6-8 Holmes chipped in with five spikes as the Americans produced 41 of them to just 30 for Germany. The set scores were 25-23, 25-16, 25-20.
Brazil and Russia await the United States in Group B games. The Americans defeated Brazil in four sets to win the men's volleyball gold medal in 2008. It was the first volleyball gold for the United States in 20 years.
In another Group B game, Serbia bounced back from its opening loss to the Americans by downing Tunisia in four sets.
Bulgaria moved to the top of Group A with a four-sets win over Poland. Italy defeated Argentina in four sets, leaving both teams at 1-1 along with Poland.