If you are concerned about demographic isolation and low mobility of low wage immigrants, look here. Among those in the American workforce with low formal education, you find that immigrant and native-born workers are sorted into different jobs. On the whole, immigrants without a high school degree fill jobs that are relatively (1) not customer facing, hence do not demand high English proficiency and American cultural know-how, and (2) more dangerous. I suspect also lower mobility potential.
I looked at 20 jobs that do not require a high school degree, totalling 31 million jobs (2014 data). Five were jobs requiring a lot of communication and imposed little or no injury risk, such bar tending, waitress and cashier. 15% of these jobs were filled by immigrants. Compare that with 15 jobs requiring limited communication and generally higher injury risk, such as construction laborers, cooks, and inventory workers. Immigrants filled 30% of these jobs. Nationwide, 17% of jobs are filled by immigrants.
One job does not fit in: personal aide jobs have high communication demands, but 24% are filled by immigrants. A large percentage of immigrant direct care workers emigrate from two English speaking areas: the Philippines and Jamaica (go here).
A poorly educated immigrant worker tends to take a job which has double the injury risk of that of poorly educated native born worker.