Looking at this from the "what industry can we make $$$ from" lens is the wrong viewpoint. Yes, the USA is pretty good at software. We are still pretty good at making cars, too. But really it comes down to our ability to innovate and create anything at all. Innovation happens at all levels. It can optimize something, giving us that 1% edge that makes all the difference, or can create a completely new industry. That's why deep capital investment in startups and academic institutions is so fundamental to our future success. We can't predict how our car, software, manufacture, agriculture, and other industries will fare in the next 50 years, but we can maximize our chances of success by being first and best at new things.
Maybe US software will collapse. Maybe Microsoft and Google will get bought by some Chinese company one day at firesale prices. If so, we need to ensure that we have new things to replace and surpass US software rather than instituting things that superficially protect it.