Go here:
C:\Program Files (x86)\Steam\steamapps\workshop\content\108600\3403180543\mods\BanditsWeekOne\common\media

Inside the media folder there will be 2 more folders, the maps folder is the one you want to open and remove (Fallas Lake, Lousville and Muldraugh+), after this you should be able to safely remove the mod from your save.

Note: fallen planes/helicopters will most likely disappear, however the damage they did should stay as well as item litter around them.