Sure, if AmTrak restructured around a lack of federal subsidies for lines in the red, the Northeast Corridor (possibly incl. Acela Express) would clearly remain in operation. It's just that a major part of the network is composed of routes where the subsidy exceeds the fare, and the fare is still too high for most people to consider.
Also, not really sure why the federal government is subsidizing $10-40+ one-way fares (receiving an average of 25 dollars in federal subsidy) as "commuter" service, even in the less-bad Capitol Corridor.