Acquisition without interaction, interaction without acquisition:

You could say that anyone can go to another country without speaking or understanding their language. You just need to use context clues, tones, and nonverbal cues to help you. 

So for an example you can go to Japan and walk into a postal building and from your context clues of on from the United States you will know to sent a letter. 

Identity of Function

One issue is that when it comes to particular situations the national language is required. So there are linguistic constraints with language. Where they can not use their native language to help when trying to apply for license or other official policies.  

 Learning begins with children’s first experiences with the families into which they are born, the communities to which they belong, and the cultural environment within which they live. By the time children start formal education at age five or six, they have already internalized many of the basic values and beliefs of their native culture, learned the rules of behavior which are considered appropriate for their role in the community. Social attitudes toward ethnic boundaries and identities influence whether students are segregated from L2 peers or have integrated learning experiences.

Language is used as source of political identification and cohesion. When immigrants come to the U.S. they are forced to give up their native language, and switch to English. A native language is parotic and unity.   

6 socially relevant dimensions that influence experiences that L2 learners may have. Age, gender, ethnicity, education level, occupation, and economic status, although they may be biological factors or economic factors, they are all also social factors of how L2 learners learn and acquire language.