Cardinals games on MLB Network would always be blacked out no matter what if you are in Cardinals territory, which is not the same as FOX Sports Midwest territory. It depends on the exact location, but people in some areas without FS Midwest can still get most Cardinals games on another FS regional sports network.
For example, FOX Sports Tennessee and FOX Sports Southeast in the Memphis area run most FSM Cardinals games. In fact, I just got their spring schedule and they will carry 13 of the 15 FSM games. They usually carry about 135 regular season ones, but I don’t have that schedule yet.
I don’t know about Southwest, but I will ask around and see what I can find out.