Complex sentence: The term "politically correct" was used infrequently in the U.S. until the latter part of the 20th century, and its earlier use did not communicate the social disapproval usually implied in more recent usage.
Split into simpler sentences: The term "politically correct" was used infrequently until the latter part of the 20th century. This earlier use did not communicate the social disapproval usually implied in more recent usage.