A.<span>United States Sanitary Commission</span>
An advantage is that it takes way less time to do it than to create a formal treaty since the President would not need consent from the congress for an executive agreement. A formal treaty can, however, last longer because it is more difficult to cancel, so if it's good, then it is also safer for it to be formal.
The declaration of independence was letting go of the English rule. While the bill of rights was putting a leash on the people in power.
