Czech is a member of SkyTeam and all paid Delta flights other than Basic Economy E fares earn one mile per mile flown regardless of price of the ticket or fare class.
Interestingly Iceland is in the same zone as the US. You can fly Delta’s seasonal service between the US and Reykjavik for 35,000 miles roundtrip in economy (60,000 in business). North America – South America is just 75,000 miles roundtrip in business class (on, say, Aeromexico or Aerolineas Argentinas). North America – Europe as well as North Africa is just 110,000 miles roundtrip in business class.