They are the same people yet there is a world of a difference between their outlook on various issues. I would say that is because in the UK Hizb-ut-Tahrir holds sway, in the US, they are largely an ignored entity. Thus the US-Pakistanis are the most educated (%age population graduates) and generally respected community whereas UK-Pakistanis are mostly, not always, a pain in the donkey.
No disrespect meant for UK based Pakistani expats, that's just how it is with most people there. I was almost killed with theories of how everything I owned was actually just an illusion and in reality my money was being held by the Jews and they could use it against Islam whenever they want. I was like:
"The Jews represent 0.2% of the global population, if they can still fu*k with the other 99.98% and never get caught, control banking, control the media, control America, control the EU, control Muslim Govts, then they deserve to keep my money!"