It is an example of ethnocentrism - the belief your culture is superior. She based the characteristics of attachment of USA cultural norms.
The strange model was found to only apply to the culture it was developed in (USA). It is an example of imposed etic, imposing other cultures with their theory.
Findings suggested that cross-cultural variation in the way infants respond to seperation is massive. Japanese children experience kangaroo parenting, where they are not left alone for the first two years of life.
Involved 32 studies in 8 countries, most striking finding is a considerable consistency across cultures - overall averages 65% secure, 21% avoidant and 14% resistant.