The Polar Star is the only heavy ice breaker. The Healy is in service but is not a heavy ice breaker. The Mackinaw is the only ice breaker serving the Great Lakes.
That makes a total of three ice breakers for the World's richest and most powerful nation. A total disgrace in my opinion.
There will be three more new heavies in a few years - uses a design from Finland, conventionally powered, will be armed with some version of the Aegis Defense System - are a few articles around with more detail.