Avery Patterson opened the scoring for the USA
A depleted Republic of Ireland proved no match for the United States as they succumbed to the hosts in Friday's friendly in the high altitude of Denver.
Shorn of a host of regulars including rested captain Katie McCabe, and the injured Megan Campbell and Denise O'Sullivan, it was always going to be a tough task against the world's number one team and so it proved.
Avery Patterson, Sam Coffey, Rose Lavelle and Alyssa Thompson were all on target for Emma Hayes' hosts.
Despite the USA resting all of their European-based stars aside from Chelsea's Naomi Girma, they were quick to assert themselves.
They threatened from the off with Thompson denied by Courtney Brosnan from point-blank range, before the Republic of Ireland goalkeeper - captaining the team on her 50th cap - turned a low Claire Hutton effort around the post.
However, the opener was coming and in the 18th minute, Lavelle picked up possession from a short corner and swung a teasing ball into the box for Patterson to nod home.
Despite some stout Irish defending, the USA doubled their lead when Coffey cut through the defence and produced a composed finish.
There was no reprieve in the second period as the USA continued to press for goals and they were rewarded just seven minutes in when Lavelle finished off a crisp move.
Number four came in the 63rd minute as Thompson managed to get past Jessie Stapleton and head for goal before curling home a fine shot to wrap up a comfortable win.
While the woodwork denied Olivia Moultrie late on, the USA laid down a marker before they play again in Cincinnati on Sunday (20:00 BST).
