Nah, rural people need the cities for finished goods, machinery, fertilizer, pesticides, and everything else. The idea that there are still hard-scrabble farmers who could band together an fight off city people is utter bullshit. It's not 1880 anymore, farming is an intensely industrialized and mechanized practice that requires huge amounts of inputs from outside the community. Rural areas simply don't have enough warm bodies to bring in a harvest without mechanization and migrant labor. If they tried to blockade the cities they'd starve before a city with an international airport did.