Iceland have once again captured the hearts of the nation with their journey to Russian Federation in stark contrast to England's more prosaic progress to the finals - but Magnusson says it can yet come good for Gareth Southgate's side.
The Irish are looking to qualify for the World Cup for a fourth time, and first since 2002.
The European country with the smallest population to take part in the Federation Internationale de Football Association world cup finals are Northern Ireland.
The Dons defender was on target in Friday's 3-0 win over Turkey, which set up the chance to clinch top spot in Group I following Croatia's draw with Finland.
Serbia are back at a World Cup finals after missing out in 2014 and with Iceland now join hosts Russia, Germany, England, Spain, Belgium, Poland, Brazil, Iran, Japan, Mexico, South Korea, Saudi Arabia, Nigeria, Costa Rica and Egypt as teams with a place at next year's tournament.More news: Sainz to replace Palmer at Renault from Austin
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Group rivals Italy, already guaranteed second place and a playoff spot, won 1-0 in Albania.
Now, the World Cup in Russian Federation will also be graced by the popular northern Europeans and their colourful fans who started a clapping trend at the Euros that is sure to make its mark next year. Albert Bunjaki, coach of the Kosovo team beaten 2-0 to secure Iceland's place, lauded the victors as "a great example for small nations like our own", and there was evident disbelief in the immediate aftermath.
With Serbia winning 1-0 over Georgia to top Group D, the showdown in Cardiff was for the prize of a playoff berth in November.
Iceland and Serbia join host-nation Russian Federation, defending champion Germany, Spain, England, Belgium and Poland in the European contingent for the 2018 tournament.
Academic and author Viðar Halldórsson who wrote "Sport in Iceland: How small nations achieve worldwide success" tweeted: "It's not genes, it's culture, organization and bunch of character!"