#11: The USA and Canada
Spanning 3986 miles on the mainland and 1539 miles between Canada and Alaska, the USA and Canada are separated by a well-demarcated border, including Niagara Falls, vividly distinguishing the two nations despite their similar landscapes.
Maintaining a visible dividing line across vast plantations between the USA and Canada might seem excessive. Yet, this characteristic boundary underscores the meticulous distinction upheld by the USA.