why Iranians say : down with usa

.Every Muslims know that today is Quds day . in this time  ,people of Iran go to the streets and chanting slogans

such as :down with america ,down with is Israel, down with Arabia ....

but if you think ,ask : why are they telling them ? they say :down with Arabia but Mohammad and Ali was from Arabia and most of Iranians names are Arabic .

and i answer : yes . we say that and also , travel to Arabia to visit Kabeh . actually , we Dont hate Arabs , we are not racist . but ! but we hate Saudis and their works , not all of Arabs in our slogans , Arabia means Saudi , not all of Arabs . in Islam we Believe that all of Human beings are equal . black and white , Arabic or american , Israeli and Iraqi are both gods creatures . according to it . Saadi Shirazii say :

PEOPLE OF USA , UK , ARABIA AND ISRAEL . WE DO NOT  HATE YOU . WE JUST HATE  YOUR Government