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.
But what is your evidence for this? Reports in the news? There are also news reports detailing the procedure that refugees must go through after being referred from UN refugee camps. Edit to add: news is not good evidence because it is biased toward sensationalism and extraordinary occurrences.
What evidence do you have for masses crossing from the US? In order to "set them up" these US illegals would have to go through the screening process to be approved for assistance, and they would be discovered to be illegal.