A state can use force in self-defense against another state or entity, but this is NOT a right, because there are limits and conditions enforced by international law*, and rights are meant to be inalienable and unconditional. You as a person can't be prevented from drinking water, but a state CAN be prevented from retaliating if they're not doing it in the right way.

But, as we see in the case of Palestine right now, people can be prevented from drinking water. It my be inalienable in a normative sense, but this whole conflict is replete with examples if Israel withholding the rights of Palestinians.

Conversely, Israel can't be prevented from retaliating. Right or not, they are going to retaliate anyway, and the international communities willingness to accept it seems to only be weakly tied to how egregious their retaliation seem to be. I guess the realist perspective you allude to is what I am getting at here, so the statement "Israel has a right to defend itself" seems to be doing a rhetorical slight of hand between factual and normative statements.

Bonus: There's further complications on how the terms country/nation/state changes things. People like to use those terms interchangeably, too, but they can mean different things depending on who you ask. I used "state" with a pretty rigid definition above. While some people use "nation" in the same way, it can alternatively connote more of a group of people with a common region, ethnicity, religion, and so forth. In that context, a nation CAN have rights, as despite the supposed universality of rights they often must be specifically expressed for vulnerable groups. That's the prime contradiction of rights as it happens—if a right needs to be enumerated like that, it's not really universal, is it?

the law isn't important when they say "Israel has a right to defend itself" they mean a moral right. Israel doesn't need a legal right nuclear weapons put you above any human laws