Costa Rica are drawn with England alongside Italy and Uruguay in Group D for next summer's tournament in Brazil.
Los Ticos are regarded as the outsiders but Campbell - who is impressing on loan at Olympiakos this season - says they are dangerous.
"England is a very strong country with a lot of good players and of course they have the chance to win the World Cup," he said.
"But they have weaknesses that can give us a chance.
"People are writing us off and that is normal because Costa Rica is a small country.
"But at the World Cup next summer, things will be very different."