A-Z Country List Western Hemisphere Travel Initiative The Department of State recommends that travelers apply now for travel documents that will be required at all land or sea border entry points as of June 1, 2009. On that date, under the Western Hemisphere Travel Initiative (WHTI) U.S. citizens will be required to present a government-approved document that denotes both citizenship and identity when entering the United States. More U.S. Passport Card The passport card facilitates entry and expedites document processing at U.S. land and sea ports-of-entry when arriving from Canada, Mexico, the Caribbean and Bermuda. The card may not be used to travel by air. More Per Diems Foreign per diem rates are established monthly by the Office of Allowances as maximum U.S. dollar rates for reimbursement of government civilians traveling on official business in foreign areas. more Country Background Notes These publications include facts about the land, people, history, government, political conditions, economy, and foreign relations of almost 200 countries and dependencies.