Start with tiny Qatar. Then guess its neighbour eith the highest CO2 emmissions per capita. Then guess the next country, etc... When you reach a dead end, go back down the line and choose the next available country connect. Finally, when you're done with continents continue onto the islands with land borders.
Overseas territories don't count, but overseas regions do
Yes: France/Brazil, Morocco/Spain
No: France/Netherlands, UK/Spain
Dubious land borders not considered: Sri Lanka/India, Qatar/UAE