Can you please help me  find any references about a horse named "U2" who has
shown in one of the Olympic games and supposedly won a silver in a Pan
American games. He is about 20 years old. Any information about this
horse would be wonderful.

A quick look gave me the following information:

He was ridden by a Brit named Carl Edwards who won the Grade A
national championships (British, of course).  The horse was then sold
to Bernie Traurigg (an American) who competed in the Pan-American
Games and won a medal.  After that the trail is a little cold.  The
horse was perhaps renamed and that will require a little more digging.

The horse has not been renamed as my daughter is currently leasing him
for riding and he is still called U2.  Do you know what years he was
shown and what medals he won?  Did you see anywhere that he had gone
to the Pan American games?

I have contacted Bernie Traurig.  I will let you know if I receive
helpful information in reply.