What is the ruling of Islamic law on accepting a job at an American company that specializes in granting housing loans and operates according to American laws?

It is not permissible for a person to work in an institution that deals with usury, whether lending or borrowing, especially if his work is directly connected to usury or involves assisting with it. This is because the prohibition of usury includes everyone who assists with it. It has been authentically reported that the Prophet (peace be upon him) "cursed the one who consumes usury, the one who gives it, the one who records it, and its two witnesses... and he said: 'They are all equal [in sin].'"