The sinking of the ship (the lusitania)
and the breaking of the Sussex pledge
Answer: the American colonists were able to confirm an official alliance with the Government of France and obtain French assistance in the war against Great Britain. ... Independence would be necessary, however, before French officials would consider the possibility of an alliance.
Explanation:
These are the formal ways...
1) Get 2/3rds majority vote in both houses of Congress to propose a Constitutional amendment and a 3/4ths vote of the State Legislature to ratify the amendment.
2) Call a Constitutional convention by 2/3rds of the state legislatures with a 3/4ths vote to ratify the amendment.