I would love to see some stats with this. What countries gain/loss the most? Which countries are the last changed? What areas are the now the most countries away from their original country?

Eyeballing the map:

For largest absolute net gain of land area, I guess Mongolia wins the cake, getting a very large slice of Siberia while losing almost no land. For a percentage net gain of land area, maybe one of the European microstates, or East Timor.

Largest absolute net loss of land area is Russia for sure. Largest percent loss is... probably Russia? Again, losing Siberia is a large fraction of its land, and nobody else seems to be so screwed by the distance.

Excluding overseas territories, there's three borders between Yakutia-cum-Japan and its current capital, Moscow, and another case of that in the far western reaches of Brazil. If you include overseas territories, well, French Polynesia is currently almost literally antipodal from Paris, and I don't really know how you would count 'most countries away' in that case, but you can't really get further than that.