I imagine that the situation in the USA is very much like here in the UK: it is usually cheaper and quicker to use road transport for single loads. Here, complete locomotives are often loaded onto heavy haulage rigs for transport to the workshops. An alternative explanation may be that the loads you have seen were railroad scrap being hauled away by the scrap merchant.
These components are often shipped to machine shops for maintenance and rebuilding. These shops may not be on the rail lines.
I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.