I believe that Congress could declare war, (though states could, ahem, not draft soldiers), could sign treaties and trade agreements
yea, i think that's it, since there are much more weaknesses to the Articles of Confederation than strengths....
The United States wanted to build the Panama Canal in order to save time and money on trading. Before the Panama Canal, people had to sail all the way around Africa in order to get to the other side of the world, which costed much more money and took a lot longer. The US owns the canal because of the Hay-Bunau-Varilla treaty, which gave the rights to the USA to build and manage it.