They wouldn’t need to do animation over seas. They have great animation software in their studio, which because of South Park’s visual style they don’t get to use “properly” very often. But it’s capable of excellent animation very quickly, and of course because of their schedule doesn’t do much for most of the year. They could easily be doing two full length movies a year with that software and their people in their protracted off seasons.
The trouble is that the rule, “You get what you pay for”, applies just as much to high tech gizmos as it does to old fashioned hard work. The high tech stuff can only give you so much. If you want beauty and subtlety, you have to do it the old fashioned way.