Patur aval assur:
I would vote to get back to the topic and to your quote from the Baal haTanya.
I don’t recall it being pointed out that things like whether or not to flee Europe before WW II are really questions of halacha, not political questions. It was well-known that America was dangerous for yahadus at the time, and that E”Y was under threat of attack from the Nazis. In fact, the Brisker Rav himself left for E”Y because of the potential spiritual threat of Russian occupation despite his fear of physical danger from the Nazis if they were to have reached E”Y.
There were parts of Europe that were not attacked until very late in the war. Had Hashem willed it, the war could have been over much earlier. Then there’s also the schar viOnesh aspect, etc.
Taking a particular set of actual circumstances without considering the many variables, both known and unknown, and then extrapolating that to “mai ahanu lei rabbanan” is, at the very least, foolish and short-sighted.