You can't in practice do that: a country may be in several time zones (Russia is in nine time zones, and the USA is in six for example).
You are much better off looking at a list of time zones (which is what Windows uses) and the calling the TimeZoneInfo.ConvertTime method:
DateTime now = DateTime.Now;
DateTime usaEST = TimeZoneInfo.ConvertTime(now, TimeZoneInfo.FindSystemTimeZoneById("Eastern Standard Time"));
Console.WriteLine(usaEST);