It is probably a combination of things. Regulatory environment and the fact that many of these companies are US based means it is easier to roll it out there first.
your right its a combination of things
from 2009-2014 the percentage of americans holding bitcoin is far superior to other countries (they got on the boat first basically). now other countries are getting on board. EG china getting onboard in 2013 and although some of us brits were already onboard from 2010-2011 onwards. the pace was really slow. mainly due to the fact that us lucky brits had a thing called 'faster payments' meaning we were never waiting around 3-5 business days for pounds to clear in bank accounts.
so we had less need for bitcoins.. but now that we are seeing our own banking system get screwed up, and with HMRC being able to just take income tax out of our accounts if we have over £5k in the account, and possible negative interest rates.. we are seeing more and more reason to get onboard the bitcoin boat..
