OK, I admit, destroy is a way too strong a word here. Rather than being destroyed, the US economy is on the way of becoming a 3rd world economy. Something like Brasil. Or Honduras. Your choice.

What is the main difference between the US economy and the economies of less developed countries? I mean now, not 50 years ago? The answer is simple: Silicon Valley. Nobody can match the rate of innovation coming mostly from Northern California. 

Why is it happening? Brains. There are 3 universities in Northern California pulling the best brains from all over the world: Berkeley, Stanford, and California Institute of Technology (Caltech). These brains create innovative companies, go to work for these companies, they created Silicon Valley as we know it. 

What do you need to do in order to destroy Silicon Valley? Restricting the flow of brains. It's much easier done than you think.

Step 1: restrict visas for foreign students. Already done in 2018. Should I mention that these three universities only accept the brightest of the brightest? Why would the US Government restrict the brightest from our universities? I have no idea. But it's done.

Step 2: restrict work visas. First of all, visas for an internship. Not long ago, students could receive an internship visa almost automatically if they have a job offer in the US. Now it's almost impossible. And, of course, H-1B visas, which allow foreign employees to work in the US. Again, now it's practically impossible to get an H-1B visa after the internship visa expires, the employee has to go to the home country and apply from there. The number of H-1B visas is very limited, so again, if a bright student somehow managed to get an internship visa and started working for some innovative US company, after some time he or she has no choice, but return to the home country. Of course, the current government has an explanation: we want America and Americans first. The only problem is that is a lie. Foreign contractors, not necessarily the brightest, are easily and without many restrictions get L1 visas (transfer within the company). 

Step 3: start trade wars and break up the Internet. We live in a globalized world. You can't fence yourself and be a competitive economy. But the current government started trade wars with China and the EU anyway. And now it's trying to create barriers on the Internet. For 30+ years the US tried to keep the Net open and available for everybody, now the government behaves almost like the Chinese government. US government ordered video service TikTok to sell US operations to a US company or to be shut down. Not many people know the history of Presidents' rage: TikTok users pretended to sign up for Trump's rally in Tulsa, OK, and, of course, didn't come. US-based TikTok users. Now the government tries to tell us that TikTok sends user data back to China. Any proof? You can easily analyze network traffic. If it's encrypted, get the warrant and analyze it before encryption. We have the US government behaving like some African government.

Of course, there is inertia. Of course, there are thousands of world-class companies in Silicon Valley that aren't going anywhere any time soon. But the damage is done. You can expect the rate of innovations to go down, you'll see less innovative companies created here. Decay takes time.

And remember, without Silicon Valley, the US is a 3rd world economy. There is nothing else that would make it outstanding in the world.