Why was the US so suspicious of the soviet union as to not let them in on the manhattan project but had a british mission at los alamos/quebec agreement/etc?
The hatred can't because of someone like klaus fuchs since israel routinely stole/spied on US without any damage to their relationship.
Why did the US view communism as such a major threat?
Remember the the U.S./Soviet alliance during World War II was strictly a marriage of convenience. Relations were shitty before that; they just realized that Hitler provided them with an overpowering reason to come together on a temporary basis.