>>1939647>>1939905>the same factors that led to its decline in our reality would still have happened The railroads would have more tools with which to fight back, like they historically got in the 1980s.
Even the railroads that weren't terribly passenger-dependent, like the Union Pacific, still weren't calling for divestment of passenger operations, and were actively maintaining and investing in new equipment into the 1950s. More freedom to adjust their cost structures would only enhance that process, and their competitiveness for the freight and passenger markets.
They would still see closure of track and declines as aircraft and automotives took customers and market share, but not to the extent/as fatally as they did historically, so that the overall network would be larger and more viable. Even when they turn over passenger operations to a national company (which would almost certainly happen), that entity would start with more equipment, better maintained equipment, more passengers, and more viable routes than Amtrak got. The USA wouldn't be Japan in this scenario, but it would have passenger usage that didn't round to zero, and likely a higher share of freight value on rail as well.