Hi Photogenic,
First off, congratulations on your excellent English and command of the English language. Second, your knowledge of German steamers and their roundhouses etc. is outstanding.
Back to the good old USA. American steamers never had it that good. Union Pacific had huge amounts of labor to take care of its steamers and keep them fit. Same for the large RR's. PRR even had its own Steam Locomotive Evaluation Laboratory for engines that were repaired, modified, home built, etc. Classic story is of the roundhouse personnel that needed to deliver a steamer at a certain time. The timing was not right and the engine had not come up to full air brake pressure, and so, could not stop on time and fell into the turntable pit. A very embarrassing situation.
The surviving steamers, still in operation, at Union Pacific are kept in really good shape by hand to this day. Still a VERY labor intensive, backbreaking form of labor, but as their people say, very rewarding and they admit to being a "dying breed". All of their personnel were trained by the old timers that knew it all, and now just they alone survive.