sorry, fact is few things are cheaper to create and replicate than software. Having investment before product, customers, and revenue provides advantage for some types of business models. It enables "failing-fast"; the "go big or go home" approach. Its useful/necessary for an arms race when many are going after the same model at the same time.
Silicon Valley is an advantage if your startup user/customer base includes and is led by U.S. users/customers. If not, Silicon Valley may be a disadvantage for understanding opportunities for innovation.
I am an American having lived in Shanghai for 8 years. Most profitable web models in China are ones evolved in China by Chinese. Sure some of it is copied, but that is part of evolution.
So if the U.S. economy is going to take a backseat in growth relative to others, China and Brazil being good examples, then go where the growth is.
In these faster growing markets, you can for the moment leverage your American earning potential to save enough quickly to pay people in China or Brazil to bootstrap your startup. VC money is harder to come by in these places, but you can fund it yourself easier than in the U.S.
Another point to keep in mind is targeting opportunities that are not going to be an overnight boom. Try thinking several years ahead of the curve a bit and finding a model that grows slow and steady in a country like China or Brazil. If your vision is only 6 months out, then many others will have the same vision and stamina to go for it. I think the real heroes are those that think longer term with what is initially niche markets. These guys can build slow and steady without VC. I'll call this the "traditional" approach. In economies like China, this traditional approach still works ;).