In June 1963, when president John F. Kennedy was given an ecstatic ovation by German crowds for his dramatic "Ich bin ein Berliner" speech, he remarked to an aide that any future American leader feeling discouraged need only be told: "Go to Germany".

Two decades later, Vice President George Bush found the streets in the same allied country decidedly more hostile. Driving to a hotel from ceremonies marking 300 years of German migration to America, the Bush motorcade was bombarded by rocks, bottles and paint-filled balloons tossed by hundreds of anti-American protesters.

To be sure, many Germans of every political stripe were appalled by the mayhem. A few outraged citizens of Krefeld rushed up and spit on arrested protesters as they stood handcuffed, then cheered lustily as they were carted away in police vans.

Yet the striking contrast in the two visits 20 years apart speaks volumes of how German attitudes, particularly among the young, have shifted toward the United States. More fundamentaly, it shows how much West Germany has changed in a generation.

The Berliners who roared their approval to Kennedy's speech were profoundly shaped by their ordeal to survive as an island of freedom and prosperity 110 miles inside East Germany.

The favorable, almost adoring sentiments showered on the young American president reflected intense gratitude for rescue in the hour of need. In the years after the war, and a decade later during the Berlin Blockade, American food and relief aid provided a lifeline of support that many elder Germans say they can never forget.

For the older German generation, including Chancellor Helmut Kohl, the CARE packages and the Marshall Plan, followed by West Germany's incorporation into the Atlantic Alliance, serve as crucial foundations that support a lasting affection for the United States.

Young Germans born after the war hold no personal stake in such powerful impressions. The era of their political awakening has witnessed Vietnam, Watergate, a succession of failed or weak American presidencies, the demise of d,etente and the specter of nuclear war.

At the same time, they have grown up amid comfort and wealth radically different from the material hardships endured by their parents. A generation has reached maturity knowing only times of booming growth, plentiful consumer goods and educational subsidies that extend student life into the mid-thirties. It is no wonder that there is a yawning generation gap in West Germany.

As the memory of the war recedes into the past, the attitudes of modern, affluent young Germans have begun to take hold throughout much of the society.

The vaunted German work ethic no longer seems true. The average work week in West Germany is about 32 hours, one of the lowest in Europe. Fifty percent of German workers crave leisure time more than better jobs or salaries.

Yet such material success has not reaped greater happiness. A nationl survey conducted by the respected Allensbach Institute showed only 15 percent of West Germans are "very proud" of their work, compared with 84 percent in the United States.

In other ways, the West German social landscape is rapidly changing, even if its political nature within a divided nation has remained relatively stable.

If Kennedy came back today to give his speech in West Berlin, he would find a city largely populated by elderly pensioners, Turkish migrant workers and German youths who have flocked there to escape the draft.

In recent years, some of West Germany's most violent displays of anti-Americanism have occurred in Berlin. The flourishing community of alternative life styles there has spawned a hard-core group of protesters. The Kohl government charged that many of those who assaulted the Bush convoy came from Berlin to disrupt the visit.

Among the vast majority of German youths, who abhor violent tactics, there are still stubborn suspicions that U.S. policies lie behind many of the world's troubles.

At the Krefeld rally, where 15,000 gathered peacefully to demonstrate against new nuclear weapons, a smorgasbord of leaflets could be found excoriating U.S. policies toward Chile, South Africa, Nicaragua, El Salvador and Turkey.

The tendency among German youths to blame the United States for most problems is not uncommon, or even unwelcome. Indeed, it is cited as a vindication of U.S. power, influence and commitment to democracy--backhanded praise for the fact that Washington is more open and amenable to reform than Moscow.

Such ambivalence may be inevitable in a country struggling to find identity while separated by barbed wire and a concrete wall from the rest of the German nation.

Kohl takes pains, as a stout Atlanticist, to reassure his U.S. and European allies that "we are not wanderers between two worlds." Yet he also exalts the goal of reunification, rejected by friend and foe, by insisting that Germans can never accept the permanent division of "their fatherland" into two states.

And with his country lying on the East- West fault line and 17 million Germans living under communist rule, he must still pursue a dialogue of cooperation with Moscow.

For West Germany, 20 years ago and today, generations past, present and future, political fate seems a perpetual dialectic of contradictions.