Should Congress mandate that every US citizen who leaves the country,?
Congress has already done so: 22 CFR 53.1 - Passport requirement; definitions. 53.1 Passport requirement; definitions. (a) It is unlawful for a citizen of the United States, unless excepted under 22 CFR 53.2, to enter or depart, or attempt to enter or depart, the United States, without a valid U.S. passport.