MLB is constantly trying to make baseball more entertaining for fans. Interleague play, DH in both leagues, ghost runner on second, pitch clock, homerun swing off for tie games.

Free of charge here are some a couple changes that I think would give MLB a big boost on the american landscape:
1: Change the shape of the field to a large rectangle, with a goal line on each end of the field.
2: Instead of nine players on a side, switch to 11.
3: Change the shape of the ball from a small sphere to an oblong air filled pigskin.
There are other changes that could be worked out along the way, but I believe these would be an extremely good start.
Your welcome baseball.