First of all,Dropdown is something that gives user a choice to select different items. If you are aimed at single item,DropDown list won't makes sense here for country as you are not providing user to select country.
Further, if you don't want to go with ip then another solution is based on Culture info. See this link.
Blocking an Entire Country from accessing the website In ASP.NET[
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Once you get the response e.g. US.Get country name and proceed further.
Google Analytics Country Names[
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Remember, in any case,you can not get 100% accurate results as there are some limitations with every approach.
Regards..