Well not a pessimist, for an American i may be an optimist, also I am looking at History here. The Roman empire lasted for a 800years, the Greeks before them atleast 500years, the British lasted for 200years and even Maurya lasted for 180years, India as power lasted for well over 2,000 years with very powerful and rich empires. This is history, the USA is hardly 80years old as a Super power, the courage, grit and character of the country is very intact, what makes an nation is its heart. USA still has an very competative culture and i dont see such a people go down the drain.
Power is not divinely ordained or distributed by some "Wheel of Law" where it grants power equally to every civilization for a certain duration, then it declines. Although everything is cyclic, i can not read anything in the spokes of time, i dont see the required disillusionment of Character we saw in the Soviet Union or the lack of grit that we see in certain nations. So if i see some signs of weakness that i can read then i will change my mind till then all this ups and downs dont matter in anyway, this is not even as serious as the Great depression of the 1920s.