Do you think Google making 66% of their revenue in the US is a sign that they are too dependent on the US market?
I don't think so. Google has plenty of room to grow internationally. And that percentage is coming down as they expand internationally. Eventually, the US will likely represent somewhere around 50 - 55% of revenue. Does that seem like a lot?
I think that's a reasonable number by analogy. Google is just a large marketplace for ads. Comparable as a market to the world stock market. Guess what percentage of the total world stock market the US is? A: 55%
As Google matures, the breakdown of Google's revenue by country will mirror the total economic activity in that country.