Some ways by which early 1915 CP Italy substantially changes the WW1 strategic equation in favor of the CP:
-The Anglo-French shall be forced to redeploy at least about 20-25% of their total forces on the Western front on the Alps. This substantially accelerates the timetable of French manpower crisis and mutines (and please note that when Italy joins the war, the Gallipoli fiasco is already well underway, so those men can't be salvaged to plug the holes on the Western front).
-An Italian expeditionary corps deploys in Albania and ensures full encirclement of Serbia. No Serbian soldier shall escape, this makes the Salonika front unfeasible, trhe Balkans shall be a CP playground, Greece a CP-friendly neutral and Romania is very likely to join the CP.
-After Serbia collapses, 100% of Austrian manpower can be used against Russia. Combined with CP Romania, this substantially accerates the timetable of Russian collapse.
-Egypt finds itself in a strategic vice, Britain shall have to deploy additional forces to cover it, which shall be unavailable to help the French.
-As a the sum result of those factors, we can totally expect that Russia (or less likely France) collapses within 1916. Therefore, Germany sees victory close enough that does not restart USW. This, combined with the shift in US public opinion created by a larger CP block, ensures American neutrality. No US troops to relieve the manpower-starved French when the full sum of German, Austrian, and Italian manpower is thrown on the Western front. As a result, CP offensives achieve a strategic breakthrough within 1917. France collapses.
-UK blockade loses effectiveness as trade restarts by land and American public opinion turns more and more against it, as they want to restart trade with the CP-dominated continent. CP offensives in Egypt and Persia. The CP start USW with the tacit approval of America, by now a friendly neutral.
-Britain is forced to accept a compromise peace.