There are two places in Chapter 4 where answers to this question may be found. The first is on pages 30 and 31 (this is according to a search of Amazon’s searchable paperback edition). The next is on page 38. Both passages show that there was a fair amount of anti-Semitic feeling in Roosevelt’s administration, though there is, of course, no way to quantify the amount of such feeling. So, while we cannot give an objective answer to the question of how pervasive the feelings were, we can say that Larson cites a number of anecdotes that demonstrate ant-Semitic feeling in the Roosevelt administration.
First, he shows important officials in the State Department writing things that seem very anti-Semitic. Larson quotes the second highest official in the department as complaining, with regard to Atlantic City, that
This place is infested with Jews.
He writes of another important State Department official, saying that
After a trip to Detroit, he described the city as being full of “dust, smoke, dirt, Jews.”
Second, Larson cites Colonel Edward House, a friend and close advisor of President Roosevelt. House did say that the government wanted Germany to be less harsh to the Jews. But he also made it clear that he thought they were partly responsible for their troubles. Larson quotes him as saying
The Jews should not be allowed to dominate economic or intellectual life in Berlin as they have done for a long time.
Thus, it is clear that there was a great deal of what we would see as anti-Semitism in the Roosevelt administration. This would make it hard for any American ambassador to work effectively to help the Jews in Germany.