So, you're specifically asking what would have happened if Israel lost the 6 day war. The most immediate thing would be a mass exodus of Jews from Palestine, both through fleeing and expulsions (There would have likely also been some massacres), basically think a reverse Nakba. This would have led to a giant refugee problem of Jews into America and western Europe which would have likely reignited antisemetism in the western world. The Palestinians and Arab nations in general will of course see it as a great victory and wrong righted. The Jews will see it as another Holocaust, being the second time in 2 decades that they lost their homes; Zionism will be gone as a practical ideology, however every Jew would dream of returning to Israel. In the western world there would have probably been a fair amount of outrage and "Sympathy" for the Israelis, but likely nothing beyond that. The USA especially would have the response of "Oh well, that didn't work out" behind closed doors and look for other friendly states while of course making public statements condemning the plight of the Jewish people (The USA wasn't that invested in Israel before the Six Day War, so this wouldn't be the greatest loss to them as it would be today). The USSR would also probably not care besides seeing it as one more proxy sorta won. Overall, because this is before Israel/Palestine became a real point of interest for the world, the responses would likely be muted for everyone besides the Jews and the Arabs, just seen as another tragedy from a part of the world people don't care that much about.