The first attempt at focusing on the Central American illegals was 2006/2007 when Bush and the GOP congress increased spending on border enforcement to end Catch and Release of the OTMs.
That led to the problem of detaining the women and children OTMs with the men, which required congress to pass legislation separating the two groups. And that led to the most recent problem of the women and children OTMs from central America flooding the border.
When the border patrol apprehends an illegal Mexican in the border zone, they can be returned to Mexico without consent, detention, or legal hearings. Because Mexico readily accepts them.
But it is different with OTMs. They can't be returned to Mexico because Mexico won't accept them. Instead, they have to detain them, have hearings, then get the country of origin to accept return of the OTM. Its a lot more expensive dealing with OTMs than it is with Mexicans, especially if the OTM is a woman or a child.
It would have been a lot better/cheaper if Congress had been able to reform immigration policy in 2006.
While I'd agree that the numbers of Mexican (state citizens) may have diminished, the aid, encouragement and assistance provided by the Mexican Government has not in my opinion. We've all seen the pictures of the glory trains transiting the entire north-south breadth of Mexico carrying those OTMs as well as the tunnels, the semis, the tankers and so on.
I'd also grant that there are a lot of other venues for entry into this country from ports, shorelines, to tankers and semis, etc. all the way to our own DHS now chartering flights to these OTM countries and picking them up! However, as a country with a known policy of support for, assistance to and encouragement of illegal entry into the United States, Mexico has not diminished its efforts in my opinion.
Lastly, I'd certainly agree about Mexican citizens being easier to return - if our government (this Administration were only inclined to do). The main problem right now with Obama and his ilk is one of pandering for future votes, coupled with a complete demographic makeover of this country to keep on getting those votes so they can stay in power forever.
So we should have surrendered the country in 2006?
McCain/Kennedy was a disaster and would have resulted in the the country being overrun.
As it is we still have a fighting chance to retain the rule of law.