This is how history works. Japan was not our enemy until after Pearl Harbor. Russia was not our enemy until the Cold War began. Events and decisions establish enemies. Prior to events and decisions there are potential enemies only, and the purpose of diplomacy and an effective defense is to keep potential foes just that.
Defense requires no enemies, it's insurance.
Where and when Americans are weak is the best answer. The Next War, projects five possible wars of the United States, with North Korea and China, Iran, Mexico, Russia, and Japan, and each within the time frame of the next 10 years. Diminishing strength will invite adversaries to emerge, who will challenge American interests. We don't maintain a strong military force to conquer or coerce others. Secure peace through strength, drop your guard, get punched.