I also notice this generally when fighting people across the Atlantic, in SC5 it was possible to fight people in America and have most fights be pleasant, but in SC6 it's often way too laggy which makes Namco's decision to remove the region selection from ranked extremely questionable.
i dont know man in my experience i play fine with people from NA while im in EU, not all of them but the ones with a 3 bar connection are just fine, you can feel the delay in inputs but its not really that bad.
Also the region selection removal was a request from the community i was not happy at the beginning as well, but i have noticed that it has not really impacted me in a horrible way so now im oke with it.
I play on Xbox. I haven't actually compared the games in detail regarding just input lag, but just by memory I don't feel like the lag when offline is significantly higher than previous games. I'll take your word for it if you think it's worse, but I don't think it's enough to explain the difference in lag when online.
I have been thinking about getting a PS4 solely for SC6, since it's near impossible to find casual rooms on Xbox forcing me to play ranked to find opponents, which I hate. PC could be an alternative, but I'm unsure how well SC6 functions under Linux.
Try to get it on PC rather than PS4. i bought a PS4 only for SC6 but looking for matches takes too long, on PC i get matches much more often thats at least my experience in EU.