Italy isn't in the map pool anymore, but you can download the map from the game's Workshop and work with that. Here's the direct link: https://steamcommunity.com/sharedfiles/filedetails/?id=88419...
Once the download is complete, right-click on the game in your library and go to Properties, then the Local Files tab and then select "Browse Local Files". Navigate to the csgo>maps>workshop directory. Folder "884196682" is the one containing the map, so open it and copy the .bsp file. Paste the file in the maps folder. Once that's done, launch the game.
While in the main menu, open the console and enter the command "map cs_italy". Once the map loads, select the T's and once you spawn in, enter the command "mp_warmup_end".
Now the achievement requires 100 round wins, but you can speed this up tremendously, by entering the following string of commands:
mp_roundtime_defuse 0.025; mp_roundtime_hostage 0.025; mp_freezetime 0; mp_maxrounds 1000; mp_round_restart_delay 0; mp_restartgame 1
Now sit back and wait for the achievement to pop!