I had been flying professionally in the UK for 21 years before I went to America. For 21 years I was taught that the TA should be the highest obstacle within xx miles of the airfield plus 1,500 feet plus 10%. So it was that the UK ended up with God knows how many TAs.
Along came jet aeroplanes that climbed so fast that they had gone through the local TA before the captain even had the chance to sniff his first coffee.
So it was that the London TMA came up with a standard TA of 6,000 feet, which had nothing to do with terrain or safety height but which gave us a fighting chance to at least smell the coffee before doing anything drastic.
I first went to the USA in 1972 when I was a member of Mrs Windsor's private airline. As a Brit, I was aesthetically appalled by their approach to the TA problem by adopting a universal TA for all of 18,000 feet.
This, I assume, is Mount St Helens + 1,500 feet + 10% (or something very similar). Apart from the problems of Victor Airways and Juliet Airways, this was actually a beautifully simple solution.
In other words, it didn't matter if you were flying in Hawaii or Alaska or even Florida, your chances of hitting Mount St Helens were 'nil'.
So why are we Europeans so averse to change?
Perhaps there is a certain faction out there still who would like to reintroduce QFE?
As someone has already pointed out, a TA of 18,000 feet in most of Europe would take care of Mont Blanc etc. (As a matter of historical interest, Air India hit Mont Blanc twice; once with a Constellation and once with a 707).
So why not go with 18,000 feet?
I for one would definitely go for it.