Much of the democratic world would like the United States to remain the pre-eminent global power. But with the US apparently committed to strategic overreach, that outcome risks becoming unlikely. The problem with America’s global leadership begins at home. Hyper-partisan politics and profound polarisation are eroding American democracy and impeding the pursuit of long-term objectives. In foreign policy, the partisan divide can be seen in perceptions of potential challengers to the US: according to a March 2021 poll, Republicans are most concerned about China, while Democrats worry about Russi…