I would have thought that the US has been the world economy’s engine for several decades now. Why? Because Americans consume so much and they buy much of the stuff which they consume in the rest of the world, thereby stimulating economic activity there.
Germans are not known as consumption addicts and they certainly don’t import so much more than they export.
I may be wrong but I would have thought an engine is that part of the car which makes the car move. Wouldn’t Germany be Europe’s engine only if it consumed a lot more and if it bought the stuff they consumed in the rest of the world, or at least in the rest of the Eurozone?