St Louis did better than most, even as NYC remained loyal enough to buy cars whose bodies rotted while some of the one huge Budd order soldier on as the oldest subway cars in service inNA.
The compression failure of N-S may also turn out to be the last effort at "fully armored tank" passenger cars in the US--IINM Caltrain has some sort of waiver. I believe that Brightline, by virtue of engines at each end they are not required to have the coaches built as 'cab cars' were spec'd for the CA/midwest joint order.

As to 'orphan' equipment, GE did some support for F-M diesels after they exited the market, and Hitachi has taken over the Breda rail business. Given the "buy American" component issue, many sparepartsshould remain available from the OEM supplier. IINM the SMART cars have US brand diesel motors.