The answer to that should be fairly obvious after Iryna Zarutska and Emily Carlson happened so recently. American and Japanese trains are not qualitatively the same. Vagrants and solicitors wander the local trains here like it is their asylum. Amtrak is a lot safer since they have conductors checking tickets, but that is still very loud and unruly.

If you'd like a more direct comparison to Japan, try Hong Kong, another place where I have spent a fair amount of time riding the trains. They also have world leading life expectancy.

Life expectancy in NYC is 82.6 vs 78.4 overall for USA. Lots of variables and such, but NYC must be doing something better than the rest of the country and I wouldn't doubt trains (and walkability) are a contributing factor.