You have the causality at least partially backwards. Why has it been so long and infrequent that the US has been in direct conflict with authoritarian adversari

You have the causality at least partially backwards. Why has it been so long and infrequent that the US has been in direct conflict with authoritarian adversaries? Because we have a giant military and a willingness to use it. Pacifism and isolationism do not work as defensive strategies.