The correct answer to this open question is the following.
Unfortunately, you did not specify at what war you are referring to. The United States has engaged in many wars and battles during its history and has received support from allies.
However, trying to help you, we are going to assume you are referring to the Revolutionary War of Independence.
If that is the case, we can comment on the following.
After the Continental Army victory in the Battle of Saratoga, the French decided to support the American colonies against Great Britain, a common enemy.
The Battle of Saratoga marked a turning point in the war in that it led to France entering the war.
The Battle of Saratoga represented a major turnaround in the morale of the troops of the Continental Army that were having many difficulties fighting the experienced army of Great Britain.
It was a hard-fought win for teh Patriots that made the Continental Army feel confident that they could defeat the English, and after the victory, European countries such as France decided to openly support the United States and sent troops and war supplies to America.
Definitively, the presence of France in the Revolutionary war was decisive for the Continental Army to win the war.
