The closest countries to the moon

Hello - hope everyone is having a jolly weekend. I had an idea about a quiz to create, which might be a bit of a challenge. You might know the "All countries in order, by area" type of quizzes; well, I wondered whether you could make one where you have to type in all countries in order, based on each country's furthest point from the core of the Earth.

My main issue is how to calculate it. For any nation, the maximum distance from the core will be dependent on two things: a high mountain helps, and you want a short distance from the equator because the Earth bulges somewhat round the middle. The distance from the core decreases by about 250 meters for every degree you move towards the pole. (The planet is actually lumpy and not a smooth curve, but I would have to ignore that inconvenient truth.) What is the best website which gives mountain locations or co-ordinates for every country - could something like that be calculated? Peakfinder.com could provide some helpful data, as it lists the heights of many mountains.

It occurred to me to name it "Closest countries to space", but I found out that space begins closer to the Earth's surface at the poles because the atmosphere is thinner there. It would be cool to call it "Closest countries to the moon", but that adds another dimension to the problem. The moon orbits within 28 degrees of the equator, so I think that gives equatorial countries an advantage and introduces some ridiculous complexity with curved geometry. The sun gives a similar issue, doesn't it, if you're not within the tropics? I considered what would happen if you made it "Closest countries to Sirius", but I suspect that certain places would still be further away because they don't face that part of space. Would be good to hear from any astronomers who can confirm all that, though, or add some other thoughts.

Of course, it's a crazy idea in the first place, and you'd have to be nuts to take a quiz like this. But it can be a fun "how-to" puzzle even if no-one creates the actual quiz. Perhaps we could choose one country each to calculate, and "crowd-fund" it that way.

What do you reckon?