Hecklers had also chanted a rendition of Neil Diamond's classic "Sweet Caroline" - a reference to McIlroy's former fiancee Caroline Wozniacki.
Two groups further back someone shouted at Sergio Garcia, who with Spanish compatriot Rafa Cabrera Bello staged a great comeback to snatch an important half against the American's top pair of Jordan Spieth and Patrick Reed, "Sergio, you suck", which led to US vice-captain Tom Lehman telling people to calm down.
The issue of American fans was thrust into the spotlight earlier in the week after the brother of Europe's Masters champion Danny Willett wrote a column in which he called them, among other derogatory things, "cretins".
A number of shouts from the galleries were evident on Friday's first day but with the tide seemingly turning in Europe's favour on Saturday the calls became louder and more frequent.
This was despite organisers making a first-tee announcement about good conduct and posting reminders about being respectful on the electronic scoreboards dotted around the course.