GM imported the Opel Kadett B, built at the recently closed plant in Bochum, Germany, into North America starting in 1966. American and Canadian car buyers weren't especially enthusiastic about these cheap little cars, but sufficient quantities were sold that they were fairly easy to find in American wrecking yards through the 1980s. Here's a '67 in a Denver-area self-service yard that managed to outlive most of its contemporaries.
Opel cars appeared under their own name in the US from 1958 to 1975, when they were sold through Buick dealers as captive imports. The best-selling Opel models in the US were the 1964 to 1972 Opel Kadett, the 1971 to 1975 Opel Manta, and the now-classic 1968 to 1973 Opel GT. (The name "Opel" was also applied from 1976 to 1980 to vehicles manufactured by Isuzu (similar to the "Isuzu I-mark"), but mechanically those were entirely different cars).
The Kadett A (above) finally appeared in 1962, and was a classic GM/Opel effort: highly pragmatic, conventional in every respect, reasonably stylish for its time, and designed to deliver a good bang for the buck. In just about every way possible, it was the antithesis of the VW: front-engine rwd, a rather tinny but roomy body, highly tossable but with a primitive suspension and ride, a very roomy trunk, and excellent visibility as well as economy. Oh, and a proper heater even! Its little 987 cc OHV four made 40 net/46 gross hp, six more than the VW 1200. Its trim fighting weight of 1475 lbs (670 kg), some two hundred pounds less than the VW, showed in both its acceleration and body integrity.