Do foreign workers have to pay tax in USA?

There is no exemption from tax unless a foreigner is working in the U.S. illegally and the employer is paying them cash or 'under the table'.

Employers generally withhold money from employees paychecks as taxes and they pay the state/IRS that money, however the employee is responsible for doing annual tax returns to ensure that all of their deductions and taxes paid are correct. In all cases, either too much or too little has been paid and the employee has to either get a refund or pay more taxes to the IRS/state.

The amount of tax you will pay on $40,000 depends on your circumstances. If you own a home and have a mortgage, this can be used as part of your deduction. You really need to speak to a tax accountant to get more specific information.

If you come to the U.S. and have a work visa the first thing you will need to do is get a social security number. This number is like your financial ID tag. The IRS and State Taxes need this number for you to file your tax returns. Besides any university will require this number before they can add you to their payroll.

You know what they say about death and taxes. You can escape from neither one.

if you live and work in usa, then for sure you gotta pay taxes to the govt in usa

how to get exemption?

You can't get exemptions.