Is having an employment card considered an illegal job in the United States?

No. If you have an employment card in the United States, you can work legally in the United States. You will not be regarded as an illegal worker, and it is not considered an illegal worker. The U.S. Employment Card is an EAD, which is a permit issued by the U.S. Immigration Service to foreigners and allows the cardholder to work for any employer in the United States, so it is also called a "work permit" and is usually valid for one year.