I got an idea, let's cut infrastructure to pay for infrastructure. You could see where some routes could maybe be shifted to states over time and maybe down the road that's worth exploring, but this would take a multi-year process and you wouldn't be able to halve the federal subsidies in one year. Florida as a big beneficiary of LD trains I could see playing ball and subsidizing its LD trains, and California would probably move to save the Coast Starlight. I don't see how you transition the hugely long east-west routes to the states though since you'd undoubtedly have some states that would act and others that wouldn't so the interested ones would have to foot the bill for the whole route. Already have some of that now with some of the existing state service. New Hampshire gets service from the Vermonter and Downeaster and doesn't participate in either, but we're also not talking anywhere near the subsidies with that example.
Florida is a big tourism state so I'd imagine a lot of ORL, MIA, and TPA passengers are passengers originate out of state. I'd want the Silver Star/Meteor being a PA resident as much as the Florida residents. Same with the SWC/CZ as I wouldn't be able to get to California without them. So those trains aren't just for Florida/California. You can tell which states aren't tourism states and which trains really are just trains that benefit specific states only and those are the ones that should be funded more by the states that benefit more from those trains.