The cumulative AIDS cases statistic in the U.S. considerably exceeds that in all First-World countries combined and this has nothing to do with Europe lagging behind.1 The correlation coefficient of new AIDS cases in the United States with that in each of France, Denmark, Canada, Netherlands, Australia, and the U.K. is 0.96, i.e., variation in the number of AIDS cases in the U.S. explains 92% of the variance in the number of AIDS cases in the other First-World countries considered. An analysis of the situation reveals that the epidemic in the U.S. stands alone, but drives the epidemic in other First-World countries (read this pdf file).
The most obvious explanation why the U.S. drives the AIDS epidemic in other First-World countries is that in the late 1970s, bathhouses became legal in the U.S., but bathhouses or their surrogates either did not exist in Europe or were closed early on.
The maintenance of an AIDS epidemic in European countries depends upon continuing visits to and from the U.S. For instance, among 78 healthy Danish homosexual men in the early 1980s, visiting the United States during 1980-1981 was a strong (7.7-fold) risk factor for a specific type of immunological abnormality related to a transmissible biological agent implicated in Kaposi's sarcoma (a cancer).2 This abnormality could not be explained by age, duration of participation in homosexual activities, promiscuity, nitrite inhalant use, or cytomegalovirus antibody prevalence or titer. A risk of similar magnitude (6.9-fold) was found in 3 men that had not been to the United States but who reported homosexual contact with a Danish man that became ill with Kaposi's sarcoma.