Petrol chainsaw

I am wanting a decent chainsaw to chop some firewood. checked on amazon had certain hasqvarna ones but not the one I wanted couldn't understand why some had the carb compliant bit and why some could be shipped outside US and some not.I am a novice to getting stuff from US that works here had got a sewing machine not realizing that you just cant plug it in and go. Thanks appreciate all the advice I can get just wondered why do they sell electrical stuff from Amazon if you cant use it here