I checked it quite precisely and the Canadian-Alaskan border is actually only made out of strait lines. The think ist that they've selected an enormous amount of mountains and drew straight lines between them. So even if it looks a little more geographic, it still never follows any single geographical feature like a river or a ridge. So alaska would be just first with 1538 mi.
I know it doesn't come close to the distance needed to be on the quiz, but Maine also has a border with Canada that appears to be a bunch of small straight lines but personally I would not consider that section of the border to be straight. (Additionally many European borders are a conglomeration of small straight lines.) I think even if the small straight lines are between chosen points it doesn't necessarily make that section of border a straight line. I am in the camp that would consider most of the Alaskan panhandle border to not be straight.
I had an idea for this exact quiz about a year ago, but I never made it happen. I love the concept! I am wondering how you got the percentages though. How did you measure the distance for the non-straight sections?
FLORIDA and GEORGIA SHOULD be accepted, as they both NOT ONLY BORDER EACHOTHER, BUT ALSO THEY SHARE a LONG Border with ALABAMA! TENNESSEE SHOULD ALSO BE ACCEPTED. This is NOT an accurate quiz w/o them. Montana too. ALASKA has a STRAIGHT BORDER WITH CANADA, SO DOES MONTANA! I reckon you do that. Yes, they may have water borders, but literally they also border other countries and states, and they're long borders still. Tennessee SHOULD BE ACCEPTED WITH NO EXCEPTIONS! ITS LITERALLY LANDLOCKED AND IT HAS NO PANHANDLES! Tennessee is like a panhandle itself. As an American from Georgia, and family in Tennessee, Georgia, Florida, Montana, and Alaska, I feel obligated to criticize this quiz w/ my dad as much as I can.