Many games, not just the original SMB2. Rock Man 2 (Mega Man 2 in North America) had one only difficulty in the Japanese release. In North America, Mega Man 2

Many games, not just the original SMB2. Rock Man 2 (Mega Man 2 in North America) had one only difficulty in the Japanese release. In North America, Mega Man 2 offered a "Difficult" option, which was the original Japanese difficulty. "Normal" was the default difficulty for the North America release toned things down quite a bit, as Capcom felt the game would be considered too difficult by the North American market. There's well documented lists of games that were significantly easier for the North American release, with only a few harder for North America.