Einstein thought the US was following in the footsteps of fascists when it got caught up in McCarthyism. He didn't think that communists were nearly as much of a threat as those who used the fear of communism to trample civil liberties. "America is incomparably less endangered by its own Communists than by the hysterical hunt for those few Communists that are here," he said. And it seems to me that one could substitute terrorists for Communists in that sentence.
But eventually our country's anti-communist hysteria died down. When it did, Einstein wrote to his son an expression of high praise for our country, his appreciation for the resiliency of the country's sensibilities.
"God's own country becomes stranger and stranger, but somehow they manage to return to normality. Everything - even lunacy - is mass produced here. But everything goes out of fashion very quickly."
*All quotes from Walter Isaacson's biography of Einstein.