The right to own guns also kept Japan from invading the US in WWII. Owning guns scares your enemies and makes the think twice.
I'd really, REALLY like to know where you came up with that idea.
There are only 2 attacks on the States that I'm aware of: a sub shelled up by Santa Barbara, CA; a few weather balloons fell to ground up around Idaho. The Japanese knew about the Gulf Stream and tried 'bombing' us that way.
Personally, I think that having a 3000 mile supply line would be a bigger intimidation.