U.S. citizens do not require a Diplomatic Visa to enter Algeria. However, a U.S. passport is required:
Your U.S. passport must be valid for a minimum of 6 months from the date you plan to depart Algeria.
Your passport must have adequate unused visa pages to allow for entry and exit stamps upon arrival and departure from Algeria. Please note that Amendment pages in the back of your passport are not to be used for entry and exit stamps or visa issuance.
TOURIST VISA: Approval from Algiers is required before a visa can be issued. This may extend processing time for several weeks.