Little and fast-to-understand test for to know the language of iPhone device:

NSString* language    = [[NSLocale preferredLanguages] objectAtIndex:0];                // en  
NSString* countryCode = [[NSLocale currentLocale] objectForKey: NSLocaleCountryCode];   // US
	
// Console Log, only for debug...
NSLog(language);
NSLog(countryCode);
	
BOOL result;
if ([countryCode isEqualToString:@"GB"] || [countryCode isEqualToString:@"US"] || [countryCode isEqualToString:@"CA"])
{
	result = YES;
}
else
{
	result = NO;
}