Washington shares a border with Canada
Alaska
Arunachal Pradesh. It shares its international border with Bhutan, China and Myanmar. Also Sikkim, it shares its international border with Bhutan, Nepal, and Tibet (China)
The state of Texas shares its southern border with Mexico.
Alaska shares a water border with Russia and a land border with Canada.
Maine, it shares a border with Vermont.
Arunachal Pradesh. It shares its international border with Bhutan, China and Myanmar.
Because the state shares a border with another country. For example, Minnesota shares a border with Canada and Arizona shares a border with Mexico. Ther term "border states" also applies to countries of one affiliation that have a border with countries of another affiliation. such as the countries that bordered the former "Warsaw pact" block in eastern Europe.
Assam shares its border with neibering state of Nagaland, Meghalaya, Manipur, Mizuram, Tripura and Arunachal pradesh along with foreign nation Bhutan, Bangladesh.
Connecticut is north of New York's maritime border
There is no Australian state which shares a border with all other states. No state except for Victoria shares a land border with Tasmania. South Australia shares a border with all mainland states and the Northern Territory.
Oklahoma shares most of Texas's northern border.