Cuba and the U.S. have the oldest Academies of Sciences outside Europe. Both countries have a long history of scientific collaboration that dates to the 1800s. Both scientific communities also share geographical proximity and common scientific research interests mainly in Biotechnology, Meteorology, and Public Health research. Despite these facts, scientists from both nations face serious barriers to cooperation raised by the U.S. embargo established in 1961 that prohibits exchanges with Cuba. The study aims to analyze the effects of U.S. policy on scientific collaboration with Cuban scientific institutions. The results of the bibliometric analysis of Cuba-U.S. joint publications in the Web of Science, and Scopus databases between 1980 to 2020 indicate sustained growth of scientific collaboration between scientists of both nations over the past forty years. The results also show that after the 1980 Smithsonian Institution and the Cuba's Academy of Sciences agreement significantly increased scientific collaboration between U.S. scientists with their Cuban peers. President Barack Obama's approach to normalizing the U.S. Cuba relations in 2015 enhanced Cuban scientific production with U.S. scientists by exceeding the number of collaborative papers published during any preceding U.S. Presidential administration. By 2020, Cuba had expanded its scientific links to 80% of the countries in the world. Cuban and U.S. scientists converted from adversaries into partners, showing that science is an effective diplomatic channel. A particularly important question for the future is how robust is the collaboration system in the face of greater political restrictions?