This is an excellent question. We know Mexico and Canada are two of the four as they are immediately adjacent. After this it gets a bit tricky. After looking at Guatemala from Texas against the Caribbean nations from the Gulf states, as well as Alaska at Russia, one sees that Russia and Cuba are the two next closest. At its closest point (the Diomede Islands in the Bering Strait), Russia is only 2.5 miles (4 kilometers) away from the US.
So the answer is Canada, Mexico, Russia and Cuba. After these would come the Bahamas.
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Actually, the Island of Bimini (part of the Bahamas) is closer to Florida than Cuba is, so the Bahamas should be ranked 4th.
Chile is the southern hemisphere country that is closest to the US. Both countries have territories near the 90°W line of longitude at their closest points.
The four largest countries by land area are; Russia, Canada, China and the US.
The closest southern neighbor would be Mexico.
Norway is the Scandinavian country closest to the United Kingdom. The distance between the two countries at their closest points is about 300 miles.
That would depend on where you are, which you didn't include in the question.
The four countries closest to Japan are China, Russia, North Korea, and South Korea.
Mexico (borders the US) and Cuba (90 miles from the US).
The closest country to Japan is Russia. At the closest distance, the countries are only about four miles apart.
Chile is the southern hemisphere country that is closest to the US. Both countries have territories near the 90°W line of longitude at their closest points.
Bermuda is a British territory in the Atlantic. It has no bordering countries. The closest countries to Bermuda are the US and the Bahamas.
The closest countries to Italy are: Austria, France, Vatican City, San Marino, Slovenia and Switzerland. You can copy and paste this link of Italy's closest countries: http://www.wordtravels.com/images/map/Italy_map.jpg
Great Britain, France, Italy, and US
The sovereign states or countries closest to the US are Canada and Mexico
The four largest countries by land area are; Russia, Canada, China and the US.
The two countries closest to the US are Canada and Mexico, which share common borders with the US.
Canada and Mexico border the U.S.
Oh, dude, like, the three closest Spanish-speaking countries to the US are Mexico, Canada... wait, no, scratch that, Canada doesn't speak Spanish, my bad. Okay, let's try this again. The three closest Spanish-speaking countries to the US are Mexico, Cuba, and the Bahamas. Like, they're practically neighbors, you know?