Never buy a first year car, especially from an American car company.
Never say never. The 2011 models are pretty damn successful from a quality standpoint. Sure some had issues (#8 cylinder, MT82, startup tick) but the frequency of these issues seems to be in line with any potential issue in any model year. the vast majority of 1st model year owners, myself included are overwhelmingly satisfied with their 2011 cars.
I think the last 4 MYs have an excellent track record and with the amount of R&D that has gone into the 2015 i would expect more of the same. As for "American car companies", we are talking about a 2015 Ford Mustang, not a 1976 AMC Pacer