I think it will not take long until we can use a tool (or maybe an updated version of maps4cim).
There are different ways of doing it. The best way would be to just change the important part and only shift the rest of the header according to the alignements.
However, to make it easy, here is a very simplified step-by-step guide for changing a normal map to a european one by just taking the complete header of a european map:
1.: gather all needed tools, in this case: a hex editor (like e.g. HxD) (just google one)
2.: start CiM2, create an empty european map, name ie europe.map (or whatever), close CiM again (or alt-tab out of it)
3.: copy the newly created europe.map to the desktop (or a folder of choice)
4.: copy the american map to this folder
5.: open europe.map with the hex-editor - note that the header of the map starts with: "FD 77 FD C9 84 FE FE"
6.: search for the second appearance of this sequence. It should be right after a lot of zeros "00 00 00 00 00 .... 00"
7.: copy the header, from the first byte up to the last "00" just before the second appearance of "FD 77 FD C9 84 FE FE"
8.: open the american map
9.: overwrite the complete header of the american map with the header copied from europe.map - The file size may change.
However, since the complete header (including the filling zeros) is copied&pasted, the alignment of the remaining map should be fine.
10.: save and close the editor.
11.: rename your modified american map to any name desired. Please do not overwrite the original map before testing the new map in the game!
12. Go back to CiM2 and load the map in the editor.
13.: if everything worked, the map is loaded and european buildings can be built. Save the map again to be sure that the format is correct and be happy!
Be aware that every meta data is lost since the header is overwritten by our empty european map.
The header contains data like the original map name, date of creation and working duration on this map.
Errors and omissions expected, please always make a backup. Normally nothing should go wrong, and as long as backups are present, no data willget lost. However, wrong maps can cause the game to crash. So just note that I can not hold responsible for your mistakes