Um, no, Muslims declared war on non-Muslims a little over 1300 years ago. We've just been living through a 'hudna' as they call it, since oh, the last seige of Vienna, or maybe the Armenian genocide, depending on how you want to account things. When they're too weak to fight non-Muslims, they have an 'operational pause' presented to their opponents as 'peace' or at least a 'cease-fire'.
The problem is that our enemy is neither just active terrorists, nor all Muslims, but rather all Muslims who take seriously the dominant school of Koranic intepretation which holds that the violence-advocating suras have precedence over the peace-advocating suras.
For diplomatic reasons (the utility of getting those Muslims who adhere to different schools of intepretation, or who don't really care much, to be either neutral or actually allied with us) it's best to talk about being at war with 'the terrorists' 'extremists' etc. As a practical strategic matter planning ought to proceed on the assumption that all Muslims are enemies (since only a tiny minority follow another school of intepreation, and the ones 'who don't care much', while not enemies now are potential enemies.)