Everything that they thought was wrong in their lives where they were, often follows them wherever they go. Wherever anyone goes. Your perception of a place is in your head, so if it is normal conditions and you are miserable, then you will be miserable wherever you go. If it is horrific conditions where you came from and you come to the land of good and plenty, it may not even compute that our luxuries are luxuries the immigrant will appreciate. It is a drastic change. Many will be grateful but all will be scarred in some way.
An immigrant from Iraq had a problem with NSW bureaucracy. He set up a tent outside the state parliament, in the city centre of Sydney, to protest and was there for about a week before a politician finally got the ombusdman to attend to the matter. During that time, strangers brought him gifts of bottled water and food and stopped to talk with him about his problem. When a news film crew came to interview him, he said he was amazed at the freedom of speech and kindness he had received in the west - that it was more in keeping with the spirit of Islam than anything he had ever experienced in Iraq. One anecdote does not provide evidence for generalisations, but I felt touched and warmed by his way of integrating with Australian life.
I'm sure they probably do, but that's not by virtue of them being immigrants, rather them being people.
You get enough people, of any persuasion, together and there are bound to be problems. Truth be told, most of the problems with immigration have little to do with immigrants. It's usually some other policy or set of policies that pose the real problem.
All the immigrants I knew work harder than most Americans. Where I live, there are immigrants from India, Columbia, Canada, Mexico, Guatemala, Somalia, China, etc.
They are professional people---mechanical engineers, doctors, one has a transportation company, graphic artists, etc. I know other immigrants from Pakistan. The guy is a lawyer, works for an oil company. Lots of smart people with businesses.
They are here to help with international businesses, as they can speak different languages. The oil and medical field businesses are huge! We also have many chemical industries. They travel all over the globe. I wish I could go with them, but no one has invited me yet. I would love to go to India for 3 weeks.
Some go to Peru. Some work in Peru and are Americans. American go there, and immigrants work here. Weird, huh?
Our brains are impacted by the experiences we've had since birth. Within America (and most other countries) there's plenty of trauma of all kinds happening around the country every day, and plenty of returned servicemen suffering PTSD from wars overseas. Not fair to assume that only migrants have problems.