There’s a large kollel in Cleveland Heights headed by Rabbi Boruch Hirschfeld and Rabbi Grunwald (I forgot his first name). There’s also a kollel in Denver which has about 10 yungerleit, along with baalebaatim who come during morning seder. In Chicago, there are several large kollelim-Chicago Community Kollel, Adas Yeshurun (Choshen Mishpat Kollel), Telshe Yeshiva, Kollel Ohel Torah.
Also I think there’s a large kollel in Miami.