So, I went back and looked, and it was actually more nuanced than what I first posted. Pan Am did have flights to Hawaii and Alaska, although those route authorities were granted prior to either becoming a state. However, PA was considered primarily an international carrier and they were repeatedly denied the ability to launch domestic flights or to acquire a domestic competitor.

Some domestic airlines, however, were granted a very limited number of international routes. TWA launched service to Europe; Northwest Orient flew to, well, Asia. Additional Pacific routes were opened in 1969: https://en.wikipedia.org/wiki/Transpacific_Route_Case . Because UA was so strong domestically, they were refused permission to operate any international routes during the CAB era; until 1983, the furthest any UA flight went was Hawaii.