Adam Clarke on Psalms 33:12

Blessed is the nation - O how happy is that nation which has יהוה Jehovah for its אלהים Elohim; the self-existent and eternal Lord for its covenant God; one who should unite himself to it by connections and ties the most powerful and endearing! The word אלהים Elohim, which we translate God, refers to that economy in which God is manifested in the flesh.

The people whom he hath chosen - The Jews, who were elected to be his heritage, whom he preserved as such for two thousand years, and whom he has reprobated because of their unbelief and rebellion, and elected the Gentiles in their place.