What is weakness of cross-culture variation?

-Comparing attachment of countries not of cultures in Ijzendoorn's research -Compared GB with Isereal in their meta-analysis, within each country there may be different sub-cultures, which are unique in child rearing -Researchers notes that variance within cultures was greater than between countries (1.5 times) -It stands to reason that they did not collect data on attachment in subcultures whithin the countires they investigated rather than the nation as a whole