Culture - McDonald's, Coca-Cola. Spread of U.S. brands. U.S. TV shows
Politics - USA instrumental in setting up IMF, WTO and World Bank
Military - Cold War with Russia, Nuclear drop on Japan
Geography - Huge population, huge workforce and labour market. Urban population of 81%
ECONOMICS - Wall Street is centre for business globally. Dollar is world currency. Silicon Valley, potential for more wealth etc. USA donation of 11 billion USD to Europe to help rebuild post-WW2, Fordism and its spread
Challengers? BRIC nations of Brazil, Russia, India and China