"Arab" usually refers to language speakers rather than a nationality or ethnicity.
Arab Americans trace their roots or heritage to several Arabic-speaking countries: Algeria, Bahrain, Comoros, Djibouti, Egypt, Iraq, Jordan, Kuwait, Lebanon, Libya, Mauritania, Morocco, Oman, Palestine, Qatar, Saudi Arabia, Somalia, Sudan, Syria, Tunisia, United Arab Emirates, and Yemen.
Hashim, Ahmad. Arab American Festival. 2011. Flickr. Yahoo. 7 June 2015.
Cainkar, Louise. "Arab Americans." Encyclopedia of Race and Racism. Ed. Patrick L. Mason. 2nd ed. Vol. 1. Detroit: Macmillan Reference USA, 2013. 161-166. Gale Virtual Reference Library. Web. 7 June 2015.