Harrison - Ireland successfully debuted five players and scored nine tries in putting away the United States 55-19 in rugby on Saturday.
Winger Keith Earls was over within three minutes after flanker and first-time captain Rhys Ruddock took a lineout and fullback Tiernan O'Halloran beat a tackle and drew the last man.
Earls had a pair before the end of the quarter and was named man of the match on the occasion of his 60th cap.
No. 8 Jack Conan, making his first test appearance in almost two years, got the second half rolling four minutes in, scoring his try after controlling the ball off the back of a dominant scrum.
Ireland notched four tries in the first half and five in the second, and gave up three tries to the U.S., two off charge downs.
Winger Jacob Stockdale and lock James Ryan scored tries on debut, and also making their first bows were front-rower Andrew Porter, the third of the world under-20 finalists of last year.
Hooker Dave Heffernan, and back Rory Scannell, who joined his brother Niall on the field, also earned their first caps.
Ireland moves on to two tests with Japan, starting in Shizuoka next weekend.