Additional points:
1. There is a concept that being sent into Galus was a Bracho in disguise- that Hashem davka spread us out so that when Jews are attacked in one place, they will find haven in another. So perhaps it is fool-hardy to have such a large concentration of Jews in 1 place. By the way, there were close to 7 million Jews living in Eastern Europe, and another 2.5 million in Western/Central Europe prior to WWII, out of 15 million worldwide. While there were many reasons to leave Europe, no one suggested that Jews should leave because they had reached a dangerous critical mass. And let’s say they had read the hand-writing on the wall and left in millions for England and the Americas (ignoring the fact that these countries would not have taken them). Hitler had plans to conquer the world – he had maps showing how many Jews there were in the US and worldwide. Is it so ludicrous to imagine that had Hashem willed it, and 6 million needed to die, he could have conquered England and America too?
2. Yes, E”Y was destroyed twice and Jews suffered enormously during both chorbonos. Yet, the Neviim foretold of only 2 chorbonos, and then we would return to our land. It seems that Gog uMagog will involve E”Y- perhaps we are experiencing it already. Chevlei Mashiach prior to the geula. But Gog uMagog will involve the whole world- and ultimately E”Y will be saved. I rather be here when it happens. I hope those that are saying that E”Y is an “eretz ocheles yoshveha” will be able to join us in the end too.