As far as I can tell the “mostly true” (rather than true full stop) is this:

“The federal government does not have a separate, dedicated revenue stream exclusively for disaster aid,” said Joel Tirado, an institute spokesperson. “FEMA funding comes from general revenue aggregated nationally. So, it isn’t possible to know how much of California’s taxes go to disaster relief specifically.”

So basically, money is fungible, and we (CA) send the most money (absolutely, though not per capita).