Exactly. People who have immigrated from across the oceans necessarily are severing ties with their home country, and so are much more likely to assimilate to our values. Immigration form the southern border is different, because those cross-border ties make it much easier to retain the culture and values of their home countries. That is particularly true when the immigration is sufficiently rapid that assimilation does not happen. What you get instead of assimilation to our culture is an extension of their leftist culture into our country.
The way I see it (and I spent a lot of Time in Baja and have good friends there) is that in what may come as a surprise to many, There are a lot of mexicans and central/south Americans that are NOT in a big rush to get here. They like it where they are and see America as a land of fruit loops, not the fruited plain.
The PROBLEM is that the policies of liberalism have made being here, more attractive than being there, so much so that they will risk death to get here. I live in AZ along a smuggling route. The I40 corridor. I see it a lot.
Those policies have enabled two things. In Mexico, they further enabled corruption by the truckload in an already corrupt govt. Then, flush with greed and wanting more, the Mexican pols, like their american counterparts, turned to the Drug cartels and human trafficers to relocate the 'burdens' of Mexico to the labor market of modern day slavers. And despite the fact they are wearing no chains, the rape trees dotting the southern border stand in testament to the reality of very real slavery.
Those illegals as we see every election, vote Democrat. This time we apparently got lucky. Supporters elected Trump and the Dems were stopped for the moment. Now it has to be used to advantage to break both the democrats, break the Mexican govt and return functioning borders, a functioning immigration system and most importantly a functioning government to Mexico so their people are not used to serve the whims of Democrat slavemasters/can live in dignity and not be beholden totheir cohorts on the right in the free/cheap labor express.
The fallout from that accomplishment is a cascade effect across many pillars of the leftist global power structure.