For that matter, look at Europe. France has gone through 5 republics and an empire since 1789 and they got a new constitution around 1958. (West) Germany has had three governments in the past 120 years, most recently in 1945. Spain has only been democratic since 1975. All of Eastern Europe has an entirely new state since 1989. Most of the smaller western countries got conquered by Germany in WWII. Even the UK in its current state is only since 1922, although that's a little unfair since I believe that was evolutionary; the last discontinuity was in 1660 if my history is correct.
Which surprises me; the US is doing really well.