The following reference [L1 ] provides simple data files that can be imported into a Tk canvas (code to follow later). Download the world.bln file in the section
Mapping -> Mapping - XY->BLN - Blanking/boundary
. Each length of border line is labelled with its country, though I am not sure if the common border between (say) Belgium and France is labelled as Belgium, France or is in the europe.bln file twice. The source of data is UNESCO; accuracy may not be ideal (it omits the Isle of Wight off the south coast of England, which is larger than some of the other islands included).