I'll start with my own personal experience.
I spent 6 months in Salt Lake City (SLC) back in 1993. Back then, there were almost no Mexican there. Gun crime was almost nonexistent. They had just appointed their first drug task force (a small group of police). There was also very little graffiti, and even then, most of it was "Skateboarding is not a crime" type stuff.
Then I moved back there from 2000 through 2007. By 2000 there were already a lot more Mexicans there and the crime rate had risen considerably and was continuing to rise.
The Mexicans were initially relegated to the west end of the SLC valley and the west side of Ogden (the second largest city, north of SLC). During my eight years in SLC, I watched as they spread across the valley and the state.
While SLC is the largest city in Utah, Ogden has the highest amount of illegals, and also the highest crime rate in the entire state.
Gun crime became an almost weekly occurrence. It was usually Mexican on Mexican, but it was also Mexican on American.
It's more than just the crime that comes with illegals, it's also the destruction of American neighborhoods. I watched cities such as West Valley erode as the Mexicans migrated eastward into the valley. Once nice, clean, safe neighborhoods became trash strewn, graffiti covered, rundown, and crime filled. I'm not talking about some report or new piece, I watched it encroach on my house. Ultimately, I moved further east into Taylorsville. By 2007, that same Mexican created environment was encroaching there as well.
I watched cities erode right before my eyes.
The logic behind it is simple and irrefutable. Mexicans seeking "a better life" come from a run down third-world country that they can't be bothered to fix or even take care of. They come to a first-world nation and bring the lifestyle that trashed their country to the new one. The don't assimilate or try to live to first-world standards in any way. What I saw happen to those cities was their transformation from first-world standards to third-world standards.
As one person so aptly put it, we're importing poverty.
Add to that the shear numbers of Mexicans that are here. There are upwards of 26 million of them here, with over 600,000 arriving every year. How can such a tidal wave of third-world people not effect the country that they're invading?
Again, I'm not talking about a report or news piece, but the very effect that I've seen happen in SLC. Now, living in Boise, I'm starting to see it here.
As for simple facts, just do a Google search. You'll find the numbers. Billions spent on educating illegals in schools. Billions spent on providing welfare to illegals. Billions spent on illegals in law enforcement and the legal system. A disproportionate amount of crime, especially violent crime, caused by Mexicans. 12 Americans killed every day by illegals. And on, and on, and on.
Again, it comes back to the Mexicans and the place they come from. They can't be bothered to try to clean up their own country or civilization, but I'm supposed to believe that they'll come to the US and magically start living with first-world standards? They're not.
They will continue to spread until it become your problem, too.