That statement is a bit misleading.
First, most any consumer that is looking at cars today has no idea those Oldsmobile diesels even existed... heck, some folks may not even realize Oldsmobile existed, let alone had the single best selling model here in the country in the late '70s.
Second, while it is true to some extent that the basic design of that Olds diesel was lifted from their gasoline V8s (and they also made a V6 version, which was a chopped down V8 like many other domestic V6s), it was quite different in the key areas. Also, with the exception of the V10 TDI, every VAG diesel sold here since 1977 was also based on a design shared with their gasoline engine. You take an ALH apart down to its bare block, and it looks exactly like an AEG block. They even use the same main bearings. Another very popular diesel that was also based on a gasoline engine? Navistar's 6.9L, 7.3L, and 7.3L Powerstroke engines. Those were based on IH's old 304/345/390 gas V8s, and I am pretty sure nobody has much complaints on the durability of those diesels. Also, around that same time Mercedes-Benz was selling some really tough, reliable, durable, and frugal diesels here. These models are arguably among the best ever, near legendary, of the compression ignition road going passenger cars. So if all you remember of 1970s + diesel is GM, too bad, there were others that were very good. My 1979 Rabbit was an excellent little machine.
FWIW, EVERYONE sells diesels in other markets. And if they don't make one, they put someone else's diesel engine under the hood of their car. For political and consumer reasons, we have not had much choice of them here, and thanks to VAG's recent chicanery, likely will have fewer in the near future.