Territorial occupations/annexations not recognized by the United
States Government are not shown on US Government maps.
Why don't you include information on entities such as Tibet or
Kashmir?
The World Factbook provides information on the administrative divisions of a country as recommended by the United States Board on Geographic Names (BGN). The BGN is a component of the US Government that develops policies, principles, and procedures governing the spelling, use, and application of geographic names—domestic, foreign, Antarctic, and undersea. Its decisions enable all departments and agencies of the US Government to have access to uniform names of geographic features.
Also included in the Factbook are entries on parts of the world whose status has not yet been resolved (e.g., West Bank, Spratly Islands). Specific regions within a country or areas in dispute among countries are not covered.
What do you mean when you say that a country is "doubly landlocked"?
A doubly landlocked country is one that is separated from an ocean or an ocean-accessible sea by two intervening countries. Uzbekistan and Liechtenstein are the only countries that fit this definition.
Why is the area of the United States described as "slightly larger than China" in the Factbook , while other sources list China as larger in area than the United States?
It all depends on whether one is looking at total area (land and water) when making the comparison (which is the criterion used by the Factbook) or just land area (which excludes inland water features such as rivers or lakes).
Total area (combining land and water)
United States = 9,826,630 sq km
China = 9,596,960 sq km