this is wrong. jews are just as monotheistic as muslims are.
no, they associate partners with Allah by ruling by other than he has revealed.
Quran 5.64
The Jews say: "Allah's hand is tied up." Be their hands tied up and be they accursed for the (blasphemy) they utter. Nay, both His hands are widely outstretched: He giveth and spendeth (of His bounty) as He pleaseth. But the revelation that cometh to thee from Allah increaseth in most of them their obstinate rebellion and blasphemy. Amongst them we have placed enmity and hatred till the Day of Judgment. Every time they kindle the fire of war, Allah doth extinguish it; but they (ever) strive to do mischief on earth. And Allah loveth not those who do mischief.
this saying Allah's hand is tied up is negating true belief in Allah and saying his power is limited and is therefore disbelief.
Quran 2.135
They say: "Become Jews or Christians if ye would be guided (To salvation)." Say thou: "Nay! (I would rather) the Religion of Abraham the True, and he joined not gods with Allah."
here Allah is clearly telling us they associate partners with him in various ways.
Quran 9.30
The Jews call 'Uzair a son of Allah, and the Christians call Christ the son of Allah. That is a saying from their mouth; (in this) they but imitate what the unbelievers of old used to say. Allah's curse be on them: how they are deluded away from the Truth!
this is the heresy where some jews believe one of their kings to be a Son of Allah, may Allah bring such people to a true understanding of man's relationship with Allah - i.e ISLAM.
there are many other verses in the Quran where it is pointed out the jews and christians are disbelievers, they have broken their covanant and so will not be a rightly guided people until they return to the correct path which is islam, the true monotheistic faith.
peace be upon those who follow righteous guidence,
Daw'ud