Answer: to make treaties with foreign nations
Explanation:
The United States government has the sole power to negotiate with foreign nations for the sole purpose of uniformity.
Treaties with foreign nations have to be binding on all states and the best way to do so would be if the Federal government negotiated on behalf of everyone as opposed to each state going about it on their own.
When a treaty is made with a foreign nation, Congress needs to ratify it for it to be binding.
