History does not support this assertion. The Israelis are very determined and capable in self defence.
You might not be aware but the super right wing Israeli's are basically all in favor of reducing Israel's reliance on the US because they feel this reliance puts too many restrictions on Israel since that support gives the US some ability to politically moderate Israel's actions.
> Let's put it to the test. No US support, only sanctions. Let's see how far they get.
This was basically the situation immediately after the founding of Israel when Israel was at its weakest. Israel was historically the most aggressive when it had the least amount of outside support.