The Astra is a good $2-3K dearer than a Cobalt, with an absolutely lacklustre engine/transmission combo. That said, the scantily marketed model distributed by a handful (by old GM standard) dealers has consistently outsold the Pontiac G5, even being an ostensibly discontinued model.
I don't think the hatch is a problem. Price, marketing and content are. With the right price and content levels, this could have been the vehicle the warmed Americans up to hatches. The original Focus, if memory serves me well, sold surprisingly good as hatchback.