The result of rattling sabers in Central America

What the Reagan people assumed about Central America when they came to Washington a year and a month ago is more true today than it was then.

Many Western experts and diplomatic observers think that what was curable then may be irreversible now. Here are the highlights of the present situation.

The rebels in El Salvador enjoy increased popular support, have become more radical, and are doing far better in the fighting.

The revolutionary government in Nicaragua is more radical, more closely tied in with Cuba, more anti-American - and very much stronger militarily.

The Cuban armed forces have been resupplied by Moscow with later and better weapons, have strengthened themselves by bringing home from overseas many of their best battle-seasoned fighters, enjoy more general public support, and are braced to resist any attempted United States invasion.

The Reagan people came into office sounding as though they would soon be invading Cuba and taking new military action against the revolution in Nicaragua and the rebellion in El Salvador.

But then nothing substantial was done to back up the threats. In effect, Washington first frightened the radicals in Central America, then gave them more than a year in which to perfect their organization, to appeal for more help from Moscow (which apparently came), and to use latent anti-''Yankeeism'' to improve their popular position at home.

Words and phrases that in Washington sounded more or less routine and obviously had no strategic plan behind them had practical and undoubtedly unintended results in Central America. President Reagan and Secretary of State Alexander M. Haig Jr. had talked about ''drawing a line'' and eliminating subversion in Central America ''at its source.''

It sounded ''tough'' on the American hustings. In Central America it was taken to mean that the Reagan administration might mount a military expedition at least against Fidel Castro in Cuba.

The Cuban government reacted by first seeking diplomatic exchanges with the Reagan people. When that got nowhere and the Washington rhetoric escalated, they took fright. By late summer and early fall of last year the Castro people in Cuba apparently expected an invasion. At one time the Cuban armed forces went to battle stations and manned the beaches, the airfields, and other likely points for a US invasion.

According to a Western diplomat stationed in Cuba, the majority of the Cuban people a year ago were friendly toward the US or at least not anti-American in spite of years of Castro anti-American propaganda. But the talk of a possible US invasion has aroused their sense of patriotism. The net effect of the talk in Cuba has been to give Senor Castro the role of defender of the motherland. Apparently he has more popular support now than he could have enjoyed a year ago.

A similar side effect is to be noted among friends and allies. In West Europe the effect of the rattling of the American saber in the direction of Central America has been to arouse sympathy for the Central American radicals. European capitals seem to have difficulty understanding the difference between the Soviet attitude toward Poland and the US attitude toward Cuba, Nicaragua, and El Salvador.

To a European there is a tendency to think that if the Poles should be free to be Poles, so too should Cubans, Nicaraguans, and Salvadorans be free to be themselves.

This is even more true of the Mexicans.On Feb. 21 President Jose Lopez Portillo of Mexico went to Managua, the capital of Nicaragua. He said there that US intervention anywhere in the region (Central America) would be a ''gigantic historical error.'' He asserted that recent events in El Salvador and Nicaragua ''do not represent an intolerable danger for the fundamental interests and national security of the United States.''This political intervention by the Mexican President in the US attitude toward Central American radicalism came precisely one day after President Reagan in Washington had said at his most recent press conference that the present Nicaraguan Army ''is of tremendous size , beyond anything they might need for possible defense.'' He said the arms came from Cuba.President Lopez Portillo said:''The Central American and Caribbean revolutions are, above all, the struggles of poor and oppressed peoples to live better. To say they are something else, and to act as if they were, is counterproductive: You finish up achieving what you wanted to avoid.''The Nicaraguan Army at the end of 13 months of Reagan foreign policy is obviously larger than anything needed to defend against any threat from neighboring Latin countries. But right-wing Nicaraguans are organizing armed forces for an attempted counterrevolution. They are training in camps in southern Florida, so far with the at-least-tacit consent of the authorities in Washington. The Nicaraguan Army is preparing to defend itself against such a right-wing invasion backed by US armed forces. Independent sources confirm Washington assertions that there has been a considerable new supply of Soviet weapons to Cuba during the past six months and also a steady flow of weapons from Cuba both to Nicaragua and to the rebels in El Salvador.A year ago the rebels in El Salvador had mounted what they called their ''final offensive.'' It had fizzled. The rebels had apparently expected a popular uprising in their support. It failed.The government of Jose Napoleon Duarte was at that time still pushing a land-reform program which had broken up the largest holdings and distributed the land among bona fide peasants. It was popular and beginning to be successful.A year ago the revolutionary government in Nicaragua was still relatively moderate. It had not yet been taken over by the hard-core communist element, or by the pro-Cubans. It was not a client of Fidel Castro. The Mexicans say that it is still not decisively in the hands of the hard left. But it is certainly much farther over and much more indebted to Castro now than it was then. Had the Reagan people continued a benign attitude toward the Nicaraguan revolution and pushed for continued reform in El Salvador there would have been less political polarization than has since taken place. And there would not have been the motive for the military buildup in Nicaragua and Cuba.As things are, expert observers suspect that the radicalization has gone so far that Washington can no longer reverse the tide by the methods it is using. If it could use the total armed forces of the US, it could of course stamp out Castroism in Cuba, Nicaragua, and El Salvador. But popular, congressional, and allied oppositon to use of US forces for such purposes is now stronger than ever.

Can Castroism be wiped out with the forces which the administration could use?The moral of the story is that it is unwise to threaten and then wait 13 months before acting.