Slightly off topic, but you've got the SS all wrong. GM actually sold way more of those than it was shooting for. In the early part of the last decade (2001 to 2003 timeframe), they negotiated a new labor deal with the union at the Holden plant in Elizabeth, South Australia. I don't remember all the details, but the important one for the SS is that they guaranteed a certain number of units produced per year, and they were selling fewer than that in the two primary markets (Australia and the Middle East). So they had to find a way to sell some Holdens elsewhere.
The first product of that deal was the Pontiac GTO, based on the Holden Monaro. Then, Bob Lutz pinned his turnaround of Pontiac on the G8, which was based on the Holden Commodore. The G8 actually sold way more than was needed to meet the minimum production for the labor contract, but was only sold for a year and a half before GM went into Chapter 11 and shut down Pontiac. Then, they came out with the Caprice PPV, also based on the Commodore, but the fleet sales for that weren't really meeting the production goals, so they decided to bring over the top-of-the-line Commodore SSV as the Chevy SS.
By the time the SS debuted, they knew they were going to be shutting down the factory for good in 2017 and not renegotiating the contract, so they were just running out the clock on the existing contract. They only needed to sell 2000 SSes a year to meet the goal, and they ended up selling around 3000 a year for MY14-16 and over 4000 for MY17. They didn't even market it beyond using the nameplate in NASCAR, because they were exceeding their goals already with a $0 marketing budget.
So the SS wasn't canceled due to poor sales. It was always a temporary solution to meet a labor contract until they could shut down the last car factories in Australia. The problem wasn't poor sales of the SS in America, it was poor sales in Australia of the car the SS was based on.