Whenever used in sections 39-855 to 39-876, the word county or counties shall be construed to include municipal corporations as well and to include any commission or authority which may be established in any county or counties; and whenever the governing body of any county is specifically directed or empowered to perform a given act or function it shall be deemed a grant or direction for the corresponding governing body of a city or village, or any commission or authority which may be established within any county or counties, as the case may be, to do likewise. Any county in the State of Nebraska may build or construct or aid in the construction or complete construction of any highway, wagon, vehicle or automobile bridge within the State of Nebraska and any adjoining state across any river, navigable or nonnavigable stream, forming a boundary line between any county within the State of Nebraska and any other state of the United States.