Answer:
the United States failed to ratify this treaty.
Explanation:
When the protocol was first signed in 1997, president Bill Clinton signed alongside all the other leaders. But Congress didn't ratify it and then in 2001, President George Bush Jr rejected the treaty altogether. Bush claimed that the protocol was inefficient, but did not take any alternative measures.
The protocol went into effect in 2004, but evidence shows it has been unable to curb the emission of CO2.
In 2013 there was another attempt, but this time neither Russia nor the US ratified it.
