I disagree, sicily played a small role in both the other films, more screentime was in the US and Vito Corleone's base all his life was NYC. It would have been fitting to end it there. The only reason it would be fitting is because the mafia comes from sicily.

With Connie, I understand everything written, but you have to agree, her TRUE motives for wanting Vincent in the chair are not clear. I still get a bit of revenge for Carlo in there, and reducing Mike's power is her plan.