This paper examines the impact of rising U.S.-China geopolitical tensions on three main dimensions of science: STEM trainee mobility between these countries, usage of scientific works between scientists in each country, and scientist productivity in each country. We examine each dimension from a “U.S.” perspective and from a “China” perspective in an effort to provide evidence around the asymmetric effects of isolationism and geopolitical tension on science. Using a differences-in-differences approach in tandem with CV and publication data, we find that between 2016 and 2019 ethnically Chinese graduate students became 16% less likely to attend a U.S.-based Ph.D. program, and that those that did became 4% less likely to stay in the U.S. after graduation. In both instances, these students became more likely to move to a non-U.S. anglophone country instead. Second, we document a sharp decline in Chinese usage of U.S. science as measured by citations, but no such decline in the propensity of U.S. scientists to cite Chinese research. Third, we find that while a decline in Chinese usage of U.S. science does not appear to affect the average productivity of China-based researchers as measured by publications, heightened anti-Chinese sentiment in the U.S. appears to reduce the productivity of ethnically Chinese scientists in the U.S. by 2-6%. Our results do not suggest any clear “winner,” but instead indicate that increasing isolationism and geopolitical tension lead to reduced talent and knowledge flows between the U.S. and China, which are likely to be particularly damaging to international science. The effects on productivity are still small but are likely to only grow as nationalistic and isolationist policies also escalate. The results as a whole strongly suggest the presence of a “chilling effect” for ethnically Chinese scholars in the U.S., affecting both the U.S.’s ability to attract and retain talent as well as the productivity of its ethnically Chinese scientists.