Sweden and South Korea both suffered disappointing 2-1 losses in World Cup tune-up matches against teams who failed to qualify for Russia 2018.
Peru, who will play the Socceroos, France and Denmark in Russia, prevailed 2-0 against Croatia with Andre Carrillo scoring in the 11th minute and Edison Flores hitting in the 48th in Miami.
Sweden lost 2-1 at home to Chile, courtesy of a 90th minute goal by debutant Marcos Bolados.
Chile went ahead in the 22nd minute on a beautiful strike by Arturo Vidal, blasting into the far upper left corner from the edge of the box.
Sweden responded just seconds later to even things 1-1 with some wonderful passing. Ola Toivonen was the final beneficiary of the team play and hit home inside the near right post.
Sweden will be playing in Group F this summer in Russia, along with holders Germany, South Korea and Mexico.
The Asian qualifiers took the lead in the seventh minute against Northern Ireland as Tottenham's Son Heung-Min played a nice ball over the top into the run of Kwon Chang-Hoon, who struck home under goalkeeper Trevor Carson.
Northern Ireland equalised on 20 minutes when a Jamie Ward cross was directed into this own goal by Kim Min-Jae.
Northern Ireland secured the victory through a goal by 20-year-old Paul Smyth, who scored on his international debut in the 86th minute - two minutes after coming on as a substitute in Belfast.
Mexico picked up a World Cup friendly victory, getting the upper hand against the World Cup debutants Iceland, winning 3-0 in Santa Clara in the United States.
Eintracht Frankfurt's Marco Fabian opened the scoring on a 37th-minute free-kick, and Sevilla's Miguel Layun got a second-half brace.
The four teams' tests for the summer World Cup in Russia continue Tuesday, with Peru playing Iceland and Mexico taking on Croatia.