Will GM with it's short patience and attention span of an ant actually wait that long? ATS was designed and intended to conquer Europe. Waiting to effectively launch it means minimal US sales. It's not even selling to projections of about 30K a year. CTS - that's even sadder. It's a newer product and isn't even selling to CTS Sigma levels. What has GM got in these two cars - a $billion apiece? They are nowhere near amortising the cost of developing them, and trending down.
The problem with saying 'fix America first' is competitors are selling well everywhere - which gives them money to reinvest. Jaguar is expecting to sell 200K XEs a year - currently, roughly ten times the ATS in the States. That's why they can launch in Australia with three gasoline motors (all forced induction), two diesels and three trim levels - no waiting three years for the 'hot' one, the supercharged XE-S is arriving on launch. Yes, a tiny RHD country where they will sell dozens in total a month, if lucky.
And emerging markets like South America, sure, you need to round out your numbers with them, but China is used to cheap - really expensive high value goods sell a fraction of a market like England, where there are scores of millionaires at least on paper due to assets. And, they tend to be low-margin smaller engined devices due to fuel prices, congestion and yes, China has CO2 taxes. The English buy more 3-series than Mondeos. That is the market you need to crack - they are not especially sold on their own products, it's GM's biggest market in Europe (they sell more Opels as Vauxhalls, than Opels in Germany).
I cannot understand how GM could possibly think landing a competent car (wrongfooted into benchmarking a competitor whose size grew) is enough. You need more - at least equivalent sales/service experience to Lexus.
And the chassis is great - the engines driving it are not more than competent and the 2.5 Chevrolet n/a four is a Chevrolet-grade motor that does not belong in that car.
You can quibble about styling, but NVH and ergonomics and design - nope. If users as typified by car reviewers find Cue slow, confusing or hinky it needs revising.
I don't think size is the issue with ATS - except it's too small for America, really; but adding six inches to the back seat won't fix that.
It's problem is - in America, it's 80% of what it needs to be, but fixing the 20% won't give a major fillip to sales, although it'd help. In Europe, it's 60% of what it needs to be. Fixing that 40% will be harder, but the potential return is greater.