While I wouldn't completely discount cultural and business-environment differences, this is probably the most relevant part, > Another fatal flaw was that Germany's retail market is already saturated with discounters such as Aldi and Lidl, meaning that any new arrival inevitably finds itself in the midst of a cutthroat price war. Walmart's model is to do high volume at low margins with a highly optimized supply chain…
FYI to those unfamiliar with Aldi: their (grocery) stores are fairly small, run in a seriously minimalistic manner. Products are usually presented either on their shipping palettes, and/or still in volume cases - customer does some of the unpacking. Most products are "made for Aldi" or otherwise sourced from bottom-price manufacturers. Variety is nearly nonexistent. Typically (at least in every store I've seen in USA) there are only two employees at any time - one acting clerk, other stocking/cleaning. Credit cards are not accepted; before debit cards, it was cash only. Aldi seemed the last store to use barcode scanners, clerks having literally memorized the codes for every product in the store and could process checkout nearly as fast (sometimes faster) than barcode scanning. Stores are very clean & simple.
You'd be hard-pressed to beat that cost-cutting business model.