Taxable Traditional IRA distributionx are taxed as ordinary income so the tax rate depends on the total amount of taxable income that you have so the tax rate can be between 0-37%. CARES act distributions are not subject to the additional 10% penalty if under age 59 1/2.
Roth IRA distributions may or may not be taxable at all depending if you only remove your own contributions or remove any earnings.
Because you can elect to include the taxable amount a Cornonavirus-Related Distribution entirely on the tax return for year in with the distribution occurs or in equal parts over 3 years, this election can also affect the total amount of income tax that will be attributable to this distribution.
Are the States going to go along as well and allow taxation in three parts ?
Most states begin with federal AGI, so unless such a state mandates an adjustment to income to bring the year 2 and year 3 income back into year 1, which is extremely doubtful, particularly since I'm not aware of this being done with any qualified disaster distributions, the income will be spread over three years on state tax returns as well.