I don't see how that's related - the tax coffers of NYC (which is not the same as e.g. federal budget) are currently not being used to help rebuild the flooded

I don't see how that's related - the tax coffers of NYC (which is not the same as e.g. federal budget) are currently not being used to help rebuild the flooded houses in smaller cities; and it would not make sense for NYC to start using the NYC's infrastructure money for fixing problems of other municipalities.