This is a surprise. I did not know that NTA even syndicated any of the Republic serials in their chapter-by-chapter form.
I am aware of the "Century '66" package of feature versions of Republic serials. These were my introduction to many Republic serials, run on a local television station interrupted frequently by ads for local automobile dealerships.
Curiously, I don't remember "Captain America" as being one of the serials that got edited into a feature.
Link to the book:
Return of Captain America TV Pressbook