Capitalism isn’t Ayn Rand’s invention, true, and she doesn’t deserve credit for all the benefits of capitalism. Capitalism has been around before her, and would’ve been around without her, in some form. Not just in the US, but in the whole non-communist world.
That said, Rand deserves credit for her moral defense of capitalism, and helping clarify what capitalism is and what it isn’t, to some extent, in the minds of her small number of, but often influential, followers.
Some of those followers have made her influence pretty wide spread. Not among the masses that make up the nations of the world (that’s a cultural victory that is yet to be won), but behind the scenes. You have to remember, for instance, that capitalism in Asia isn’t really due to nations like SK, Taiwan, Thailand, etc. developing it on their own. The work ethic and sense of justice ingrained in local cultures was key to the spectacular economic growth once capitalism was introduced, sure, but the smooth, efficient introduction of capitalism is due to western influence and constant, careful US guidance. And Alan Greenspan, the man sitting at the center of the western economic system for several decades, during the development of the Asian “tiger” economies, NAFTA, ASEAN, the European Union, etc. was a student of Ayn Rand’s. As were, I’m sure, many others in the Reagan, Clinton, and Bush administrations, and probably even in the Thatcher, Major, Kohl, etc. administrations.
These were the people who guided the world towards globalization (which is just a moniker for global capitalism), and built a world where there’s nothing anti-capitalists on the left or right (whether they’re named Donald Trump, Bernie Sanders, Boris Johnson or even Alexis Tsirpas, as Greece so painfully realized) can do to roll it back. And, by their own accounts, they owe an intellectual debt to Ayn Rand. Most have not integrated her entire philosophy, and they compromised even on the parts they did pay attention to, but they still brought about unprecedented prosperity, and they did it by spreading capitalism and free trade.