The study looked at how U.S. government spending and tax changes affect Canada, the U.K., and Japan. By analyzing data from 1975 to 2014, they found that when the U.S. increases spending or cuts taxes, it can boost the GDP of these countries in the short term. The impact varies between countries, but overall, government spending changes have a bigger effect than tax changes. This suggests that some countries can benefit a lot from U.S. fiscal policies that aim to stimulate the economy.