This question is flawed. I believe it was meant to ask: "If you ask a random person <span>who identifies as American</span> this question, what is the probability?" etc. Assuming this is the case, it would be 93% probability.
Otherwise, America is equivalent to 4.34% of the total world population as of Thursday, April 6, 2017 (http://www.worldometers.info/world-population/us-population/). So, 7% of 4.34% is 0.3%.
