What do you think would happen if the US and all of Europe completely pulled out of the Middle East? Would Israel stay the size it is now? If not, can you really say it's "purely defensive"?
I am not sure what you are implying. Can you elaborate? Are you saying Israel would go attack its neighbors and seize land? From Egypt? Jordan? Lebanon? If so, that's an absurd proposition with absolutely no geopolitical data points to back it.
I don't think it's too absurd to imply that a country would expand into weaker neighboring countries if it could. One example where the US has intervened is Egypt -- without the US the Sinai Peninsula would surely be part of Israel right now. So yes I'd say it would seize land from Egypt, as it already has.
If the US and Europe pulled out of the Middle East it would be too chaotic to predict anything. It depends on the presence of other superpowers (Russia, China) and the pecking order that would be established between the regional powers (Turkey, Israel, Iran, Egypt + the Sunni world).
Also, "pulling out" is too simplistic. There are not only troops on the ground, but also military bases, joint exercises, weapon sales, commercial ties, industrial ties, scientific collaborations, cultural influences, and so on and so forth. Short of disappearing from the globe the US cannot just 'pull out'