"Since it goes through Google's servers, they can verify a lot of things. Whether you are logged in currently to google, have you been logged in the past, verify your activity on your IP address, etc. Even if you signed in from the same ip or ip range like a year ago, they can still tell it's you based on your previous actions."
The normal captchas have been getting increasingly user-hostile over time. The only limit on them is what users are willing to put up with, and now that Google's most profitable users don't get them that's less of an issue. In fact, having nearly unsolvable captchas is actually an advantage because it encourages users to let Google track them.
No, this is likely done with machine learning trained on real vs fraudulent user data. So they are going to be watching for much more subtle features than just being in a different region. Tons of people travel all of the world. Less people manually resent their MAC addresses or use datacenter ISPs.
"Since it goes through Google's servers, they can verify a lot of things. Whether you are logged in currently to google, have you been logged in the past, verify your activity on your IP address, etc. Even if you signed in from the same ip or ip range like a year ago, they can still tell it's you based on your previous actions."