Once a country is involved in a conflict, they cannot join NATO. You are proposing a logical catch 22 in which countries that join NATO only do so out of fear mongering (in your opinion), and countries that actually are involved in conflicts cannot join NATO, and thus will not be protected by the US. Finally, NATO countries aren’t being attacked, so unless you recognize the value of deterrence, there will never really be a chance to provide examples that fit into the framework you’ve set up.
I hope you do recognize the value of deterrence, and I also hope you recognize someone can’t provide examples of things that were prevented due to deterrence, since they never happened.