With all due respect, that's terribly naive (or, you think we're terribly naive enough to believe it.) Pollard wasn't the first, and he certainly wasn't the last.
Naive would be thinking you can conduct espionage without ever getting caught. Getting caught spying a huge risk, and unless you have an even bigger risk, why would you ever do that? What can possibly justify risking getting caught spying on the US? Israel isn't dumb, it's a simple risk analysis. Unless Israel has a bigger risk to protect against, than the US cutting off ties as a result of another polard, Israel would never do that.
Given past performance, I don't think there is any rational reason to believe that Israel risks America severing ties with it over incidents of espionage.
In any event, Israel has a nuclear deterrent, even if they like to coyly lie about it. In the fantasy scenario where America no longer supports Israel, they'd manage just fine on their own. But again, that's not going to happen. Too many Americans think it a matter of religious imperative that they and their politicians continue to support Israel, no matter what.