Unique culture of Innovation and melting point of the best brains in the world
USA is the home for the best brains in the world. It's not that the average IQ of an american is by default higher than that of people from other countries, america has successfully created an environment where the best brains of the world come and collaborate. Best of the class talents from different countries come to america and call it their home for rest of their life. That's how America can invent the best practices, products or services long before other countries can do so. US universities and private entrepreneurs are the key to this innovation journey. US has undue competitive advantage in this front which is very tough to replicate for other countries.
Strength of US Dollar
Still US Dollar is the reserve currency of the world and although its long term value may depreciate the process will take a very long time. During the Economic crisis US FED could just print money(I would say Free money) and the whole world was ready to accept dollar loans without any value depreciation of the USD. I don't think the model where US consumers continue to consume without creating similar amount of value and the rest of the world supply money and services to them is sustainable in the long term. But till the time we see an alternate global currency US dollar and as a result of that US will continue to dominate world economy.
US Military Power and strength in Global political diplomacy
US has unmatched military power and because of that it enjoys unmatched political supremacy. The might is always right and hence it can push for laws and sanctions which give them an undue advantage.
Scale of Operations
'Bigger the better' or 'Big is Beautiful' is not always true. But it is true that this american philosophy has helped america to create unique scale of operational efficiency, infrastructure development and use of Technology.
The more I see america, the stronger is my conviction that we will see more americanized world. This is not a perfect system but probably one of the most successful experiment done in this world.