Reality is such that militaries are necessary both for self defense and defense of the weak and vulnerable.
The US military has ensured peace and prosperity for billions around the world for decades given its formidable global presence.
Imagine the chaos and crime that would descends on a community without police or law enforcement. The world operates the exact same way. There will always be a most powerful country enforcing stability and global compliance, and I would much rather it be the US than Russia or China.