The rate of people moving within the United States is at one of its lowest points in U.S. history, while China has experienced unprecedented levels of domestic migration. While both are world-leading economies, these countries demonstrate stark contrasts in geographic mobility, urbanization, and economic growth. Despite these differences, social factors affect migration capabilities in both places, with some people more mobile than others. This study assesses internal migration and highlights the structural and social determinants of mobility in both countries. This article’s analysis reveals an accentuated downturn and the longest annual decline recorded in the U.S. Evidence shows declining internal migration in the U.S. primarily occurring at the local level and amongst renters. Large and expensive American cities have had significant losses of residents in recent years. By contrast, China’s “floating population” has increased as migrants move to cities. This study examines trends from 2010 to 2020 to compare the two countries regarding internal migration, urbanization, housing, social mobility, and economic growth. However, rather than simply comparing them, the paper argues that the internal migration dynamics in both countries are, to a degree, connected.