Most ICOs currently restrict Americans from participating. So if the above ratio is correct, we can see that the potential for ICO is still very large, because 3.75% is not a small number compared to the US population.
The roles of Americans are quite important in the adoption of cryptocurrency, if we really need adoption rate to grow very fast, I wonder why most icos are excluding Americans from there project when the technology of cryptocurrency is meant to be a global one, when satoshi started this cryptocurrency, he never segregated never thought there would be any country that would not need to take part in it,
It is better for American themselves to openly declare they are the ones not interested than for projects to seclude them, in fact, sometimes, when I see projects that do exclude Americans. Those projects looks to me like they are scam projects, and would not want to do anything that will involve scamming Americans easily and trigger investigation into their scam activities. Imagine what that figure would really do in the crypto market too.