Somewhat related to the issue raised in last night's debate about extending the U.S. nuclear umbrella to cover Israel, it's always worth making the point that one of several reasons it would serve Israel's interests to aggressively seek a resolution of the Palestinian issue is that it would be much more feasible for the United States to extend security guarantees to Israel under those conditions. With a peace deal in place, Israel would be a friendly democracy with internationally recognized borders -- just the sort of place the U.S. would make a formal treaty with.
But as things stand, Israel has no internationally recognized borders to guarantee. Obviously, some actions like a hypothetical unprovoked Iranian nuclear first strike would obviously go far beyond the scope of border ambiguity, but nuclear-armed Israel doesn't actually need U.S. guaranteed to have a credible threat of massive retaliation. Guarantees and formal alliances would be much more useful in a much lower-intensity setting, but country without internationally recognized borders isn't a good candidate for NATO membership or other kinds of similar relationships that might be useful to Israel.