Complex sentence: Some of the songs he wrote during this period were seen in Sweden as critical of Sweden, especially the song "Har du hört vad Svensken sier" (NO: Have You Heard what the Swede's Saying?).
Split into simpler sentences: Some of the songs that he wrote during that period were seen in Sweden as critical to Sweden. Especially the song "Har du hört vad Svensken sier" (NO: Have you heard what the Swede's saying?).