Overpass Turbo can not extract a whole country in one go so ,with the help of Wikipedia, you will need to break down the Country in to administrative divisions, States or districts.
Watch out for areas that have the same name as the capital city.
A further search for the area names around the city will be needed to get all the data for that area.
1/ open overpass turbo
2/ Replace all the code in the left hand panel with this code below
Code:
[out:json];
{{geocodeArea:REPLACE THIS TEXT WITH THE AREA NAME}}->.searchArea;
(node[highway=traffic_signals](area.searchArea);
>;
way[highway=traffic_signals](area.searchArea);
>;
relation[highway=traffic_signals](area.searchArea);
>;
);
out;
3/ In the code, replace all the words in capitals (REPLACE THIS TEXT WITH THE AREA NAME) with the area name & run. when complete, export the data as a kml file