The concept of “infidels” in Islam is a major source of confusion for non-Muslims, and would-be terrorists. The latter as good as infidels given their intent.
Contrary to some opinion, “infidels” in the Quran is used to denote ‘idolators’, not the ‘People of the Book’ i.e. Christians and Jews. The phrase ‘People of the Book’ is a nod of respect, and recognition to those that followed Holy scriptures prior to Mohammedans.
The “infidels” in the Quran are in reference to the idolators circa the Conquest of Mecca. These idolators reneged/refused to make peace with Pt. Mohammed. Hence Muslims were given divine instruction to fight back against the infidel idolators until they repented.
The Quran even mentions the name of the 5 infidel tribes that Muslims warred with. Needless to say these tribes aren’t Christians or Jews. There is no specific call to violence against Christians or Jews in the Quran, only idolators and Pagans.