It's actually very difficult to make Israel lose. Even if the Arabs had attacked at once, US and British intelligence predicted an Israeli victory in the end. Israel's military superiority was by then an established fact.
Aside from that, Israel had already built few crude nuclear bombs, and if the Arabs were on the verge of overrunning the country, they would have been used, though there is a possibility that the Soviets would have responded by nuking Israel.
Assuming that the Arabs manage to bypass this, and it is still a possibility that they would have, especially if the Soviets had stepped in, the United States would likely have prevented the destruction of Israel. And the Soviets would likely not step in for this reason.
Assuming, though, that the US does nothing and the Soviets step in, which was a possibility, Arab forces would have taken massive casualties, which would only fuel the rage of Arab soldiers further. And they were already inflamed with antisemitic propaganda disseminated by their governments. There would have been mass atrocities committed against the Jewish population, and a large percentage of Israel's civilian population would die, from chemical attacks and mass bombing raids on Israeli cities, defending their kibbutzim, and massacres committed by the invaders. This would culminate in a mass ethnic cleansing of the survivors, the executions of the Israeli leadership, and the division of Israel between the Arab states.
World Jewry is horrified and demoralized. Basically, in just 20 years, the Jewish people have gone through two mass tragedies. Jews would still be reeling from the tragedy.
Aside from that, no Israel in today's world means eventually almost no Jews. Today, Jews everywhere except Israel are intermarrying and assimilating at a rapid rate. The diaspora is declining as old Jews die and not enough are born to take their place, while Israel's Jewish population is rising. There would be only around 7-9 million Jews in the world today and dropping.