The difficulty that seems to plague America's interventions in foreign countries is highlighted in the latest news from and about El Salvador. The so-called ''death squads,'' right-wing killer groups that frustrate such reform efforts as land redistribution, are active again. They are so active - and so much out in the open - that Washington has been forced to protest and condemn them.
The latest round began on Sept. 20 with the kidnapping of Amilcar Martinez Arguera, director of Economic and Social Affairs in the Salvadorean Foreign Ministry.
The US Embassy on Sept. 23 condemned the kidnapping and called for the release of Mr. Martinez.
The embassy's statement said:
''We urge those responsible to desist from a path which is doing more to destroy El Salvador than the Communist guerrillas could ever hope to accomplish.''
An organization calling itself the Maximilian Hernandez Anti-Communist Brigade asserted that it had done the kidnapping.
Another group, calling itself the Salvadorean Nationalist Command, issued a statement criticizing the US Embassy for criticizing the kidnapping.
A third group, called the Secret Anti-Communist Army, has joined in the new practice of issuing public statements. Its latest criticized the provisional government of El Salvador for attempting to negotiate with the insurgents, which the United States is pressing the Salvadorean government to do.
The kidnapping of Mr. Martinez followed a rise in the frequency of killings, bombings, and kidnappings for which the right-wing groups claim credit.
On Oct. 3 the State Department backed up the embassy in San Salvador, saying:
''We have consistently deplored political violence regardless of its origin and, in the context of reports over the past few weeks, do so again in the most categoric terms. We support the US Embassy's statement last week against this violence.''