Two great points. The White Sox look good this year. About the Cubs, you're also right. In fact, when I was a kid, there where times when Cub fans outnumbered Dodger fans at Dodger Stadium when the two teams would play. That's become less of a phenomenon over time as those people, who were clearly transplants form Chicago, spawn native Californians.
I think the number of Cub fans nationally can be traced back to the early days of cable TV when WGN was included in many packages across the country. MLB, in the form of the Cubs, became available to areas where it had never been seen previously, except on Sat afternoon network games of the week. The Braves developed a similar national following when Ted Turner's "super station 17" joined cable packages in the mid/late 70s.
When the Braves signed free agent pitcher Andy Messerschmitt in the mid 70s, Ted Turner tried to put "Channel" above his jersey number "17" to advertise his super station. Messerschmitt was amenable, but MLB refused to allow it.