At http://www.fivedoves.com/letters/feb2013/jovial27.htm I posted about 2 years ago an article on why I believe the USA is the nation that Isaiah 18 refers to. To get to Israel by sea, one would need to go by the Mediteranean, which of course connects to the Atlantic, and pretty much the entire world. Which sea a ship comes by does not limit what nation could be a candidate, but other parts of the description in Isaiah 18 do narrow down who it could be, and the USA best fits the description of who it is talking about.
In way too many cases, people have a tendency to see America in prophecy where it is not, and where Europe or other countries on that side of the world are. But I have no doubt that this is indeed referring to the USA.
Shalom,
Joe