NB see thealx comment below!
I think you need to look at the common\data\language\tlate0.dat file as I think this is the one used - the '.cmp' files on mine do not have any Russian but there is Russian in the 'tlate' files.
Near the end of tlate0.dat there are sections headed e.g. ":TRANSLATION_PARAGRAPH Campaign Thailand Text".
At your own risk, make backup copies, all the usual, and I have not tried this myself...
1) Add a new section in tlate0.dat *before* the ':END'
:TRANSLATION_PARAGRAPH Campaign Alexander Text
ENGLISH text here - may as well paste the line from common\maps\map13\Alexander Archipelago.chc
:FRENCH text here
:GERMAN text here
:ITALIAN text here
:SPANISH text here
:RUSSIAN text here
NB the 'ENGLISH' line has no colon at the start
2) Edit 'common\maps\map13\Alexander Archipelago.chc' so the line between ":SHORT_TEXT_START" and ":TEXT_END" (where you copied and pasted from) says "Campaign Alexander Text" which I think is what makes it read your added section in the tlate0.dat file.
Note this is a complete guess but this is where I would start. I have no idea if this will work but I think the theory is good. This is completely based on what it looks like happens with map1 Thailand.
Somewhere there is probably a website with every disclaimer ever written, I include all of those here!
P.S. make sure your editor does not wrap lines, this might be OK but probably better to avoid doing