Why did the French fight so long and hard to hold onto Algeria, even to the ending viewing it as French (de Gaulle called the Algerians "Muslim Frenchmen")? What distinguishes Algeria (which was administered similarly to the way French Guiana and Martinique are today) from Tunisia, which was given independence comparatively easier?
One major reason would be that the French had been in Algeria 50 years before the protectorate of Tunisia was formed. During this time nationalism was on the rise so a stronger Tunisian identity had already been formed. I think the recent first vietnam war would have had major influence on the military options available to hold on to Tunisia.
Not entirely my terrain but I hope this at least gives a clue.