This year is the 100th anniversary of US-Korean friendship. Ironically, it is also proving to be a year in which anti-Americanism among some Koreans is most visibly rearing its ugly head.
Within a two-month period, the following anti-American developments have taken place:
* On March 18, a group of students set fire to the American Cultural Center in the southern port of Pusan, killing a Korean student who was using the library and seriously injuring three others.
* Four weeks later, following the arrest of a Catholic priest for sheltering the arsonists, the Korea Christian Action Organization (KCAO), which includes Roman Catholic and Protestant members, issued a statement demanding the recall of US Ambassador Richard L. Walker and Gen. John A. Wickham Jr., Commander-in-Chief of the Korea-US combined forces.
Both, the statement alleged, had made derogatory remarks about Koreans in public. The statement went on to condemn the ''arrogant attitude'' of US policy level officials in Korea and certain ''shameless US business practices'' relating to Korea. It called on the US government to ''recognize the increasing distrust that its Korean policy finds among the Korean people.''
The statement also demanded that the Korean government release political prisoners, end the practice of torture, cease manipulation of the mass media and stop prejudice against the Catholic church and other religious organizations.
The impact of the statement was only slightly allayed by Ambassador Walker's explanation that he had been misquoted and by the fact that many of the 42 people whose names appeared at the end of the statement, denied having signed it.
Observers point out that there has been a thread of anti-American feeling since 1945. Some of the blame for the division of the country has fallen on the United States. The presence of 39,000 US soldiers in South Korea sometimes causes friction, and a certain amount of resentment inevitably accompanies Korea's dependence on America in economic and security matters.
But to balance this, there has been very real gratitude for America's war effort during and since the Korean war. One Korean explained that as a child in the 1950s, ''I was brought up to look upon the Americans as our saviors. It would be emotionally impossible for me to go against them now.''
But today's 20-year-olds have not shared this experience. Since the brutal crushing of the Kwangju insurrection in 1980, many students have distrusted President Chun's government and so resented US support for it.
And in spite of an impressive list of democratic reforms carried out by the government last year, many religious leaders seem in recent months to have decided that these are largely cosmetic - that too many restrictions remain; that torture is still practiced in the prisons; that political prisoners are unjustly detained; and that surveillance by secret police is, in the words of one priest, ''worse than it ever was under President Park.''
Opponents of the government fear that open opposition will bring swift reprisal, that anti-Americanism is a means of indirect opposition and much safer.
The view expressed here recently by US Vice-President George Bush that human rights can best be furthered by ''quiet diplomacy'' may not have convinced the more militant of South Korea's dissidents. But the vice-president's visit was seemingly geared to open channels of reconciliation between US officials and Christian dissidents.
Assessing public opinion on political matters in Korea is difficult. There is no candid discussion of politics in the media. The distribution of antigovernment leaflets and even peaceful, on-campus student demonstrations are forbidden. Labor unions are generally ineffectual.
But most observers agree that serious opposition to Mr. Chun's government and the recent, related anti-Americanism affects only a small if vocal minority constituted mainly of students and Christian dissidents.