The main significance of the watergate affair was that it

Showed that the laws of the united states are superior to the actions of a president

The Supreme Court ruled in the 1973 United States vs Nixon case that the executive privilege protected Nixon in his official capacity as president and NIxon's accused actions were outside that official capacity. This exemplifies the american ideal that no man is above the law and that the laws of the US apply to all offices of government even the presidency.