We are all descended from immigrants. Even "Native Americans" are descended from people who crossed the land bridge across the Bering Strait thousands of years ago. And yes, the descendants of those people got screwed by Europeans and the descendants of Europeans.
As it stands today, the United States is a sovereign nation with legitimate laws and the duty to uphold and enforce those laws. The U.S., and every other nation, has the right to regulate the flow of people across its borders.
Due to geography and economic factors, the majority of people that enter the U.S. in violation of its laws come across the southern border. To the south of the U.S. lie areas that historically were colonized by Spain, thus the residents are referred to as "Hispanic" and the most common language spoken is Spanish.
On a side note, much of the western United States was once territory claimed by Spain. The residents of that area became "Americans" (in the U.S.A. sense) before the families of many of us who are of mostly European descent. There are still parts of the U.S. where most residents are naturally born U.S. citizens, and they primarily speak Spanish.
To express a desire to see the laws of the United States enforced is not a racist sentiment. If the economy Canada was as bad as Mexico's, many would feel the same about French and English speaking Canadian immigrants who entered the U.S. illegally.
The United States has several advantages. The colonists and Founding Fathers fought for independence from the colonizing nation. Through the efforts of Americans (in the U.S.A. sense) over the last 200+ years (and, unfortunately, including the mistreatment and abuse of several peoples), the U.S. has become what it is today - perhaps the best place in the world to live.
Perhaps those that enter the U.S. against its laws should direct their efforts toward making their native country a better place to live? Yes, that would frequently be a perilous path, but the U.S. is what it is today because of those who took up that yoke and faced the peril in their time so that their children could reap the rewards.
Any way you look at it, illegal immigration is an economic reality. I understand people wanting to live in the U.S. to make a better life for themselves and their families. I do not, however, think that illegal residents should have access to all the same government services as those who are natural or naturalized citizens, or services that are often not available to legal residents who are not citizens. People who enter illegally know they are breaking the law - they take that risk in order to obtain certain rewards.