Is overtime and holiday pay taxed at the same rate as "normal" pay?

Yes.

From the IRS perspective, the income earned from overtime versus holiday is not important. What is important for apply a tax rate is based on the total taxable income earned during the year. Taxable income, in general, is your gross income MINUS your personal exemptions.

The tax structure in the US is on a tier system. There is a base rate for taxes, and as your reach a certain threshold, your tax rate will increase for the portion of income that exceeds the threshold. There are about five threshold in total.
The threshold is dependent on your filing status: single, married, widowed, man of the household, etc.

yes.

in the USA, yes!

yes

If you're talking about the income tax being withheld - It depends on the company. Some companies change the tax percentage withheld when you get overtime or more than your normal paycheck. In the US, the more money you make the higher your income bracket is and the higher your income bracket the higher the percentage you pay in taxes.

j

Yes.

As it's your income.

You bet. Anything paid to you in cash (or its equivalent) is compensation, subject to FICA and withholdings.

Depending on the timing, it might seem that they are withholding more (say a large annual bonus). However, when filing your 1040 your income is totaled for the year and taxed at the appropriate graduated rates.

Good question.