The biggest deterrent for the Japanese to attack the US mainland after the successful attack on Pearl Harbor was the fact that American citizens have the right to bear arms, and that made all civilians militia.
Which is one of the reasons I support a Swiss style, military rifle, magazine and ammunition in the home of every citizen not convicted of a violent felony. I also believe that those that receive Pell Grants and School loans should be required to take a class that covers basic first aid, procedures and obligations of a draft/call-up, basic firearm safety, basic rifle maintenance, the constitution along with the bill of rights and lastly, basic firearms marksmanship.