The US only got the same version of Mario Bros. as the Japanese. This page shows the differences:
http://qbob.free.fr/releases/marioc/index.html
The FDS version of Ice Climbers does not have the baby seals either and allows the player to select from only the first 24 mountains, but he does not have to select in any order. All cartridge versions allow the player to select from 32 mountains, but he must play them in order.
Nintendo probably believes it should release the US versions of their games, in case some complains "its not the way I remembered it."
Nintendo did not remove the two-player mode from the NES Classics of Super Mario Bros for the GBA.