Can a commercial airliner be landed on a highway, e.g. Highway 405 in Los Angeles?
It's possible, assuming the section chosen has no streetlamps, signs, overpasses etc. The police can block the traffic easy enough.

However, there would be zero reason to do so. If a plane has enough control to reach the highway, and enough advance notice to find a suitable part and block the traffic then it has enough control and time to reach one of the many airports in the region. Much less fuss for all concerned, and a much better equipped crash service.

In the prairies one could set up a fighter or bomber base on a random road, but again there's no need to - there's nothing nearby that would require it, heavy bombers or commercial planes would quickly destroy a normal highway and fighters could use the many civil airstrips in the area.

In Europe the math is different - opponents are a short flight away and destroying the airbases on both sides would be a top priority in any European conflict. See "Highway strip" in the usual reference for more details.