But where is your direct evidence that software patents have anything to do with the US being "one of the most innovative software producers"?
I'd also argue that it's mainly copyright law and trademarks that prevents the kind of product piracy that is prevalent in certain countries with a less developed legal system, at least with regard to software products.
How often have you heard or read about a piece of software that someone developed only because it could be protected by a software patent, about a software innovation that would have been too costly to develop if it couldn't be protected by patents?
And on the other hand, how often have you heard or read about programmers and companies worrying about unknowingly infringing on software patents, about companies getting sued by other companies that turn whole fields of software into minefields, or about developers or companies that couldn't (afford to) implement the best known algorithm for an application, because someone else had been granted a monopoly on using that algorithm.
Patents are meant to spur innovation and thereby improve social welfare. Just because this may work in certain industries, doesn't mean that it automatically works in other industries. There's a lot of evidence that the costs of software patents to society are higher than their benefits.