"Good fortune" might be a weird phrase to use, but sure.
I think it's reasonably valid to use this excuse for, say, why the NYC subway is so far behind Tokyo's train system. Maintaining a system as old as NYC's requires so much money and time that there's little left over for upgrades.
But there's no excuse for a regional train like the Acela being so slow, expensive, and unreliable when compared to the Shinkansen. It's certainly difficult to do major upgrades in a constrained area like NYC, but upgrading tracks and signaling and the trains themselves in the mostly-open areas between (say) NYC and DC is a lot easier (even if you can't touch the last couple miles on each route due to city density, you can still make tons of improvements in between). And given that the US gov't gives Amtrak tons of money, and they still collect 2x as much as the Shinkansen does from passengers on a passenger-mile basis, it's shameful how poorly that money is managed.
There was an article posted on HN months ago that talked about per-mile transit construction costs in various countries, and how construction in the US costs so much more. I don't recall if there was a conclusion as to why, but it seemed to be a combination of gov't and union waste.