That happened in the golden era of multilateralism, after the fall of the Berlin Wall and the Soviet Union. The US realized how unfair the situation was, and took some timid steps to start a rebalancing of the situation, allowing for the creation of a competing currency.

It is not that the Euro was not a threat to the dollar, it is simply that the threat was minor then, and that it was plain and simple the right thing to do: renounce to unfair advantages in order to move to a more just world.

The US continues to unfairly abuse the dollar as world currency, and dismissing this fact can be a costly misjudgment: fair for the world, but painful for the US.