We should have tanks. The 2nd Amendment states we need a well regulated Militia, which I believe would be able to combat a militaristic force. There should be organization throughout communities specifically to counter various threats posed.
The problem is as soon as people start to organize they are labeled domestic terrorist or extremest. The term "militia" is also though of negatively in itself. States have the National Guards, but there's too much tied into the federal government for them to be counted on.