== No, the term "state line" is not always the term used. I have traveled fairly extensively and have heard it called a state border as your question suggests, and "the border," and a "the state "boundry." I think there may have been others, which at the moment I can't recall .
The California-Nevada state border.
most likely just another state but especially if it is not called an international border
a state border is the border of state
The imaginary line around a state or country is called a border.
Most likely, "Cool! We're in (insert state name here)!"
Maine IS a border state
None. A border defines the boundary of a state therefore no state will cross the border of another state.
the border state
They are not contiguous. Alaska is a part of North America, but has no border with any US State. It does have a maritime border with Russia and a land border with Canada. Hawaii is not in North America, but is a US State located in the Pacific Ocean.
All states but Alaska and Hawaii border at least one other state. Maine is the only state to border just one state.
The border state of Maryland was a central state in the US Civil War, and had the border state of Delaware on its east, the Union State of Pennsylvania to its north, and the Confederate state of Virginia to its south.
New Hampshire is the only state to border Maine.