@”Kapitán Denis” that’s true, all the sounds are pronounced the same, except there’s no dz and h in SCBM, although I think dz appears in some dialects, but I can’t even think of an example.
Now, I don’t know what part of Croatia you’ve visited. Dialects on the see side are nowhere close to the standard. But even if they were, Serbian and Croatian accents are of course different, some thin like central and western Slovak, with Serbian being western, the one with harder pronunciation.
You don’t hear that accent in the particular letter sounds but in stress and intonation, I remember we tried to teach a friend to say some phrase with rozprávať in it, he always accented that á with a raising tone, sounding like some easterner and no one down here talks like that. But I don’t have a feeling that it mostly sounds like Eastern Slovak, probably because I’m used to it.