“It was AGAINAST all the gedolim to move to the United States before WW II. “
Rabbi Yosef Eliyahu Henkin z’tz’l came to the US in 1922. Rav Soloveitchik z’tz’l moved to the US at the end of 1932; His father was already here. Rabbi Moshe Feinstein z’tz’l came to the US in 1936. Rabbi Rabbi Yaakov Kamenetsky z’tz’l came in 1937. We were blessed that just as two of the meraglim saw the truth, so did a some of the gedolim.