The last and only Opels worth mentioning, that I recall ever existing in the U.S., were the Opel GT, and the Manta series. That was somewhere in the mid-70’s, the same timeframe that saw Ford sell a Mustang with no guts and no soul, that GM came out with something called a Chevette (phonetically misspelled, of course).
A number of Saturns were based on Opels, IIRC.
And I just finished working onmy 70 Opel Autocross car!