Of course they know, and they know that the current wave is a planned invasion to fundamentally change this country forever.
Which is why as a LEGAL immigrant, I have zero sympathy for those who come here illegally, whether that is sneaking across the border or overstaying a visa. I have zero sympathy for the "Dreamers". Children of military and children of prisoners are separated from their parents all the time, through no fault of their own, but no one cries for them or invents a "crisis". Children of military, foreign service and parents who work for international firms pick up and move to new countries they don't have any roots in, aside from their immediate family, every single freaking day. Giving an inch on this issue is the camel's nose which is what the D's want. Reagan gave amnesty first and look how that turned out. The country needs an immigration moratorium and a zero tolerance policy. If you want to legalize, you must do so by applying from outside the country like everyone else, doing all the background screening like everyone else, and WAITING like everyone else. You must also take a TOEFL test and have a passing score in reading, writing and understanding English. When we lived in foreign countries we didn't expect everyone to cater to our language or our customs. Enough already.
If you listen carefully, these migrants all admit to being economic rent seekers. They want something for nothing. If they are so great, and so wonderful, we should insist they stay home and work on making THEIR country great, instead of letting them come here and be parasites at the expense of our own citizens. Every illegal migrant takes way more out of the system than they contribute, the D's are well aware of that too. They (D's) now want a growing welfare state and the illegals fit that bill.