What mistake, Sam? Which country was willing to accept the emmigration of 18 million European Jews. Certainly not America and Franklin Roosevelt. America had strict immigration quotas, AND THEY WERE FULLY EXHAUSTED every year. So there was no openings for any additional immigration to the US. And you know what Roosevelt did with ships with Jews that came here without authorization. You heard about the MS St. Louis, didn’t you?
So stop the anti-semitic canard that the rabbonim stopped anyone from coming to the US. The US was closed to additional immigration.