Which are? Having ridden on buses and Amtrak, buses go to the same places and more, cheaper, faster, with more available times, and keeping on schedule (the NE corridor may be faster and on schedule, I'm not in that part of the country-- but that would be the exception). There may be a small pollution difference but its probably negligible.
Amtrak absolutely can. Simply by raising their prices.
The iPhone revolutionized mobile phones and greatly expanded the interconnectivity of the world. And yet nobody is demanding that the general public should subsidize Apple.
They should be dropping prices, not raising them, at least for longer trips. It costs about the same to take Amtrak vs an airplane for a direct connection 750 miles away, which is ridiculous because it should be far cheaper to run a train at 60mph than an airplane at 400+mph per passenger, and trains can carry far more people than airplanes. They also need to be way faster (120mph at least, ideally faster than that) to be a reasonable alternative to airlines.
The only way Amtrak gets to raise rates is if it drastically improves service.
Trains need infrastructure all 750 miles of that trip. Airplanes need infrastructure only at each end of the trip. Thus airplanes are cheaper to run very long distances.