Larson, who joined the national team earlier this month, totaled 12 kills and a pair of aces, while Nancy Metcalf had seven kills, three aces and a block, as the former Huskers combined for 25 of Team USA's 57 points in a sweep that took just 61 minutes.
Verania Willis Lindo scored a total of seven points to pace Costa Rica and teammate Onikca Pinnock Gibbons added three points.
The U.S. limited Costa Rica to only 13 points in the first two sets combined. However, Costa Rica came back in the third set to lead 8-4 before allowing six unanswered points to the U.S.
United States plays Guatemala (0-1) at 7 p.m. (central) on Saturday night, the second of five consecutive pool play matches before the classification round.