Nicaragua improved to 5-0 with the victory, having outscored their opponents 34-6.
It was the first loss for the Americans (4-1), who dropped to third behind Japan (5-1).
The top four teams from each of the two groups advance to the quarterfinals.
In other games, Japan beat Australia 4-2 on homers from Yohei Kaneko and Keiji Ikebe.
In Group A, Eduardo Paret led off the bottom of the first inning with his second homer of the tournament, scored a run and knocked in another to help Cuba beat South Korea 4-1. The victory was Cuba's sixth in as many games and kept it tied atop the standings with the Netherlands, who beat Canada 7-3.
Elsewhere, it was, Puerto Rico 11, Czech Republic 1; Japan 4, Australia 2; Panama 8, Brazil 5; Colombia 3, Taiwan 2; and China 7, Sweden 5.
Nicaragua took the lead in the first inning on consecutive doubles by Garth and Jenrry Roa, who drove in another run with a single in the third and hit a two-run single in a four-run fourth.
Abea's three-run homer in the seventh, his second of the World Cup, put Nicaragua ahead 9-0. Garth, who entered the game with one hit in 15 at bats, completed a 2-for-4 day with a two-run homer in the ninth.
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