Another difference that we haven't seen yet. The illegal crimnal Mexican aliens that we have so far do leech on society and cost the society billions while making individual employers a little cash but, on balance, they work and work hard. In that regard, they are like our parents and grandparents, they work and will blend in and their children will be contributors. But, how about if the next 10 million wetbacks are not? How about if the are lazy, dump, passive criminals who figure the gringo dole is better that no dole at all?
Think of your Village Green with the gazebo and the 4th of July picnic there. What would happen if over one weekend 1,753 illegal aliens camped on the Green and began digging and demanding food, drink and entertainment? What if we've already skimmed the best Mexicans? What if the next Mexicans, lazy, shiftless and dumb could only bring discredit on the ones who are already here?
What do you mean "if"? In every area of southern California this has already happened. Long ago.