Just call it American manners...
Dubya at Heathrow Airport in England

From: hengist
At Heathrow, a 300-foot long red carpet is stretched out to Air Force
One and Mr.  Bush strides to a warm but dignified handshake from
Queen Elizabeth II.

They ride in a silver 1934 Bentley limousine to the edge of central
London where they board an open 17th century coach hitched to
six magnificent matching white horses.  As they ride toward
Buckingham Palace, each looking sideways and waving to the
thousands of cheering Britons lining the streets, all is going well.

But suddenly the right rear horse lets fly with the most horrendous,
earth-rending, eye-smarting fart ever heard in the British Empire,
including Bermuda, Tortola and the Falkland Islands.
It shakes the coach.

Uncomfortable, but under control, the two dignitaries of state do their
best to ignore the whole incident, but then the Queen decides that's
ridiculous.

She turns to Mr.  Bush and explains, "Mr.  President, please accept
my regrets....I'm sure you understand that there are some things that
even a Queen cannot control."

George W.  Bush, ever the gentleman, replies, "Your Majesty, please
don't give the matter another thought......You know, if you hadn't said
something, I would have thought it was one of the horses."