As turbulence grows in many countries, it is tempting to ask if there is a global hegemon that can sort everything out fairly. US President Donald Trump has threatened that his country would not defend Nato allies if they failed to spend enough on their defence. Together with new trade barriers, his words suggest that the US is scaling back its ambitions for global leadership and concentrating more on its own region. Our latest projections of national strength for 2027 take into account...