Even the history of Central America is anarchy. Public television tries to realize order from this chaos with an ambitious four-part "Frontline" report, "Crisis in Central America," tonight through Friday at 9 on Channel 26. Although not nearly so exhaustive, it was produced by some of those responsible for 1983's landmark 13-part series "Vietnam: A Television History."

Central America is seen through U.S. eyes in the report, and the abiding theme, stated up front and returned to throughout all four hours, is the dilemma presented by the region: When the United States attempts to impose its presence, it does so in the noble cause of encouraging democracy, yet is frequently condemned, by the usual condemnors, for allegedly acting in imperialistic self-interest.

In Part 1, "The Yankee Years," the U.S. relationship with Latin America is traced back to the turn of the century. Until the '50s and Fidel Castro, who is seen with his troops in Cuban jungles as Part 1 concludes, the United States was largely unchallenged in its efforts to shape or at least nudge the policies and governments of Nicaragua, El Salvador, Panama, Costa Rica and the other countries of the area.

Not that these were blissful, peaceful years for Central America. Black-and-white newsreel films conjure coups, insurrections, overthrows and bloody revolutions of the past. What humans couldn't do to foment turbulence, nature did. The survivor of a 1931 Nicaraguan earthquake tells newsreel cameras what it was like to be tossed on his head. The earthquake ironically accelerated the rise of Somoza.

There are rare views of the building of the Panama Canal, including a still photograph of Theodore Roosevelt dee-lightedly manning a steam shovel. The American presence was muscular but seemingly benign. An early silent newsreel captions one scene, "This was one of the filthiest streets in Hayti sic until the Marines cleaned it up."

Then came FDR with his "good neighbor" policy, and Carmen Miranda with her tutti-frutti hat; most Hollywood images of Latins during World War II were comic, the narrator claims. In the real world, Batista emerged in Cuba, as did dictators like Somoza and Trujillo in other countries. The United Fruit Co. threw its weight around, and in the '50s, Henry Cabot Lodge at the United Nations warned the Soviets, "Stay out of this hemisphere." But they did not.

Decidedly dry and meticulous, the documentary is careful (perhaps too careful) to tread a noncommittal ideological line, lest, God forbid, one right-wing group or another finds a word or phrase in any of it they consider either pro-left or insufficiently pro-U.S. Only those with a serious interest in the subject, for one reason or another, are likely to make it through all four hours, but they are likely to feel rewarded and edified by them as they do from little else on television.

The fourth chapter examines the situation in El Salvador and how it got that way. A chorus of anti-Communists sings an anthem translated as containing the sentiment "El Salvador will be the graveyard where the Reds will end their days." A pleasant thought, perhaps, but as this "Frontline" makes clear, no outcome is likely to be so simple or so soothing to American interests.

"Crisis in Central America" lacks the range of witnesses interviewed for the Vietnam series, and there may be too many interviews with vaguely identified and dubious experts (a sugar cane worker, a former student activist) and not enough with recognized authorities. But anything that contributes to an even fractionally greater understanding of what many see as a confounding mess is to be praised. This "Frontline" is to be applauded, if not quite cheered.