This is referring to the early battles when the jewish and christian tribes united to fight Muslims. Don't quote out of context, if the above was talking about Jews and Christians of all times, then there would be no need for these verses:
"Surely those who believe, and those who are Jews, and the Christians, and the Sabians, whoever believes in Allah and the Last day and does good, they shall have their reward from their Lord, and there is no fear for them, nor shall they grieve."Surah 2:62
"Surely those who believe and those who are Jews and the Sabians and the Christians whoever believes in Allah and the last day and does good-- they shall have no fear nor shall they grieve." Surah 5:69
"Of the people of Moses there is a section who guide and do justice in the light of truth."Surah7:159
"Not all of them are alike: Of the People of the Book are a portion that stand (For the right): They rehearse the Signs of God all night long, and they prostrate themselves in adoration. They believe in God and the Last Day; they enjoin what is right, and forbid what is wrong; and they hasten (in emulation) in (all) good works: They are in the ranks of the righteous." Surah3:113-114
"And there are, certainly, among the People of the Book, those who believe in God, in the revelation to you, and in the revelation to them, bowing in humility to God. They will not sell the Signs of God for a miserable gain! For them is a reward with their Lord, and God is swift in account." Surah 3:199