Scotland climbed to the top of Pool B after beating USA 39-16.
They were losing at half-time but scored five tries in the second-half.
The tries came from Tim Visser, Sean Maitland, WP Nel, Matt Scott and Duncan Weir.
Ireland beat Romania in front of a record tournament crowd of 89,267 at London's Wembley Stadium.
They're now the group leaders of Pool D.
Scotland's next match is against South Africa on Saturday October 3.
Ireland play Italy on Sunday October 4.