Aldi is a limited service grocer that doesn't have to deal with employee unions and costly departments like meat/deli/bakery/etc.
That is the underlying story, is that fewer Americans can afford the full service grocer (or maybe don't want to patronize due to smaller household sizes and less cooking). Also, Aldi has successfully fended off unions, which are mostly a thing legacy grocers like Albertsons and Kroger have to deal with.
And yet Aldi's prices in the states are more than 2% below Albertson's. Almost like there actually is more room for improvement?