You can bet that with the converter removed, it's going to be unpleasantly loud; so loud that the operator is likely to be as light on the go-pedal as ever she was.
The greatest risk for such a circumstance, with respect to CO danger is enclosed areas and stagnation while not moving.
For normal driving, with the average number of traffic lights, the level of stagnation is quite low. Traffic in the area will stir up a wind, ambient weather will often be not-calm. There's not much snow with which to enclose the vehicle, preventing another type of closed area.
The risk is extremely low, therefore, conceivably non-existent.
With a poorly tuned engine, there could be a risk of fire, although converter fires are much greater than spark-ignited fires from a chopped-open exhaust system. Don't park on dry grass with the engine running and zero out that risk as well.