This plays well with his love for almost trivially easy businesses, like Coca Cola. The simpler it is the easier it is to predict. "You want a business than can be run by an idiot, because one eventually will".
Buffett has a good understanding of trade relationships between the countries, he wrote a good piece on the US trade imbalance many years ago. He probably has an excellent understanding of the bond market. But he can't predict where will this go, so he doesn't use it as a basis for his investment decisions.
Any links for that? Would like to read it.
Note that this was before the 2008 crisis which did affect the picture. Although it seems US is in a comparable or even worse state, yet again.