I have not been able to find the context of the quote. Yes your point is valid it may be in context to the US's industrial and military abilities. But he never wanted to fight the US in the first place so in many ways he could have meant both concepts.

I am sure that if the US had ever been or is ever invaded the forces WILL have to worry about the armed citzens. Armed citizens have been the heart of many a revolution or resistance in our worlds history.