If you insist they give up their culture immediately you will be seen as trying to take away their culture. Just like how gun rights advocates perceive attacks on gun culture.
Solidarity is a normal reaction to real or perceived hostility. In history the social pressure to assimilate resulted in immigrant collectivism in order to support each other; Chinatowns, little Italy and a myriad other ethnic enclaves formed partly because of this pressure.
I was really drunk last night. So I opted to stop talking.
But your asking for proof of the people not getting caught. The link I gave you would be the closest you can get to that. That is an increased amount of people crossing the border. That is an increased amount of people being caught. Obviously, there are no stats for the people not being caught.
But these people being caught, are being fast tracked. They are not going through the same process as legal immigrants. They have no benefit to us. They had no benefit to the US. They never bothered to get citizenship there. We are spending resources to process these people. Then we are taking our tax money to provide for them. All for people who skip the tedious process of getting into our country properly.