Thank you for your question. Please allow me to assist you and provide you with some basis of information before you decide whether or not you can bring a claim against your employer.
Typically as per IRS regulations:
When Social Security and Medicare Taxes Apply Outside Of U.S.
In general, U.S. social security and Medicare taxes continue to apply to wages for services you perform as an employee outside of the United States if one of the following applies:
- You are working for an American employer which includes:
- The U.S. Government or any of its instrumentalities
- An individual who is a resident of the United States
- A partnership of which at least two-thirds of the partners are U.S. residents
- A trust of which all the trustees are U.S. residents
- A corporation organized under the laws of the United States, any U.S. state, or the District of Columbia, Puerto Rico, the Virgin Islands, Guam, American Samoa, or the Commonwealth of the Northern Mariana Islands (with respect to the CNMI, refer to Revenue Ruling 80-167).
- You perform the services on or in connection with an American vessel or aircraft and either:
- You entered into your employment contract within the United States, or
- The vessel or aircraft touches at a U.S. port while you are employed on it
- You are working in one of the countries with which the United States has entered into a binational social security agreement (also known as Totalization Agreements), and the agreement provides that your foreign employment is subject to U.S. social security and Medicare taxes.
- You are working for a foreign affiliate of an American employer under a voluntary agreement entered into between the American employer and the U.S. Treasury Department
But likewise be aware that "f you are permanently working in a foreign country with which the United States has a social security agreement and, under the agreement, your pay is exempt from U.S. social security tax, you or your employer should get a statement from the authorized official or agency of the foreign country verifying that your pay is subject to social security coverage in that country.
If the authorities of the foreign country will not issue such a statement, either you or your employer should get a statement from the U.S. Social Security Administration, Office of International Programs, at the address below. The statement should indicate that your wages are not covered by the U.S. social security system.
This statement should be kept by your employer because it establishes that your pay is exempt from U.S. social security tax.
Only wages paid on or after the effective date of the totalization agreement can be exempt from U.S. social security tax.
Generally, under these agreements, you will only be subject to social security taxes in the country where you are working. However, if you are temporarily sent to work in a foreign country, and your pay would otherwise be subject to social security taxes in both the United States and that country, you generally can remain covered only by U.S. social security. You can get more information on any specific agreement by contacting the United States Social Security Administration. You can get more information from the Social Security International Program Web site.
If this is a purely international position and you pay taxes in the country where you work, then the lack of withholding is valid. Then there is no basis to bring a claim.