Checkpoint64 has a preset for American Truck Simulator: it already knows where the save folder is, backs it up automatically and keeps earlier versions. Everything this site has on American Truck Simulator:
American Truck Simulator
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Save file location
Windows:
%USERPROFILE%\Documents\American Truck Simulator\profiles
macOS:~/Library/Application Support/American Truck Simulator/profiles
Linux:~/.local/share/American Truck Simulator/profiles -
Sharing with friends
How to share your American Truck Simulator world with friends, from playing live to taking turns when the host is offline.