The US has a huge military presence around the world. Isolationists in the US think it’s a poor investment, suspicious that it’s a form of imperialism, while interventionists in the US think the US presence protects allies and contributes to stability in the world, and if the US withdrew, other countries would fill the power vacuum. Indeed, empires have always existed, and the US might be considered kinder and gentler than empires of the past.
For more on this topic, see http://www.thehistoryreader.com/military-history/u-s-military-bases-worldwide/
US military presence abroad is just one prong of its international influence. American media and technology products permeate the world, as do fast food, auto manufacturing, pharmaceutical products and many other goods and services.