For each fiscal year concerned, the Administrator shall allocate to each State, in accordance with regulations and the total sum appropriated under this subchapter, amounts to be made available to the States for the purposes of this section. Regulations governing allocations to the States under this subsection shall give due regard to (1) the criticality of the areas which may be affected by hazards with respect to the development of the total emergency preparedness readiness of the United States, (2) the relative state of development of emergency preparedness readiness of the State, (3) population, and (4) such other factors as the Administrator shall prescribe. The Administrator may reallocate the excess of any allocation not used by a State in a plan submitted under this section. Amounts paid to any State or political subdivision under this section shall be expended solely for the purposes set forth in this section.