Hi Steven,
We are using some heuristics about the IP address of your machine to determine if you are coming from the U.S. or not. If you google “how to check your ip address” you should see an answer under the search box that tells you what yours is… if you include that in an email to us we can try to figure out why our software thinks your IP is not from the U.S.
Thanks for your interest in our study!
Merrie
I sent a screen grab of my IP result and will wait to hear back, thanks for the info though.