If you pick Teemo in ranked as anything other than a counterpick, you really just set yourself up for failure against any competent player. Any half competent jungler will shut you down early, and any half competent top will counterpick teemo with one of several popular or in the meta champs that counter him: jax, renekton, shyv, rumble or ryze to name a few. Heck, even vlad counters him.
And if you play him mid, enjoy comparable range and hard cc, along with constant visits from jangle, to make you the saddest little puffball in existence.
He's a scrubterror. Annoying to deal with, but easily beatable if you know what you're doing.