Complex sentence: Prior to this single the band mostly charted only in the US and the UK, and this song was the band's first charting in many countries outside the US and the UK such as Australia, New Zealand and most of the European nations.
Split into simpler sentences: Prior to this song the band mostly charted only in the US and the UK. It is the group's first to chart worldwide in countries including Australia, New Zealand and most of the European nations.