There was a time, however brief, when GM’s Saturn division was set to be a sister brand to Opel.
Of course, this was not long before Saturn was killed off during GM’s bankruptcy. But GM liked the idea of a "Euro" focused brand in the US, so Buick was called in as the replacement. The Opel Insignia became the Buick Regal, and the plan has so far worked very well. In fact, the next-generation Regal, set to arrive in 2017, looks like it’s going to be imported directly from Germany to US shores.