The commercial builders last steam locos were mostly purchased through UNRRA and/or US Marshall Plan aid to a number of countries.
France, and some other states purchased directly.
Simply put, due to wide spread industrial damage in WW2 there was too much that needed doing in a short period, for European and Asian countries with loco builders to cope with the world's needs. This impacted underdevelopped nations that normally bought rail goods from developped
European and Asian sources. For they were cut off from these normal suppliers, since the sources were unable to keep up with home country demands, much less foreign demand.
Furthermore, the end to colonial dependancies starting to occurr then , allowed the UK, and France to feel freed of reponsibilities to many areas of the world needing replacement of run down industrial goods of all kinds.
So there was a Canadian/American boom in foreign steam loco orders
lasting into the opening portion of the decade of the 1950s. ALCO, the
combined B-L-H, Vulcan , and CLC sold several thousand steamers in
this period to markets that they normally were too costly to serve.
These locos were essentially "plain jane", unsophisticated designs built to a few standard plans produced in classes of several hundred locos. The
French ordered several hundred mikes , of their design, that were the
best of these engines, in my opinion. That is subjective, of course, and
others have different prototype favorites.
For what it is worth, the Reading (K-5s in '48)and CanPac built modern 4-6-2s after all but the N&W had ceased producing steamers for themselves. The Reading was asked for quotes to produce steam locos for UNRRA , but declined to bid , because they had decided to deep six all the facilities and the workforce serving steam - 'ASAP'; after deciding to dieselize in 1949.
The last locos built by the big three for US common carriers included Berks , but also had some anachronistic compound 2-6-6-2s for C&O
coal mine runs. Old and tried designs, amid the "Superpower".
Good-Luck, Peter