Think of it this way. What good is being a member of a club if there is no control over who can join? Being a "member" implies that certain benefits are bestowed upon them and that there is exclusivity to the membership, The members decide who can enter the clubhouse. The same is true for being a citizen of a country. One has certain rights and privileges bestowed on one as a citizen of the country to which you pay taxes (membership fee); particularly, the decision who may enter the country (the clubhouse).
This goes back to the biological concept of territoriality. Animal mark their turf and defend it so as to claim their rights to the prey in that territory. A further extension of this is private ownership of property. What good is it to own a farm and anybody can come by and take its fruits and vegetables?
This concept of "exclusivity" or "private property" even extends to our personal lives. When people marry, the contract binding them together promises exclusivity of themselves to their mate; otherwise why bother getting married? Believe me the tax deductions are not a good reason for marriage.
We have a contract with our government (the club leaders) which states that they will protect us from all enemies, foreign and domestic. Their job is to protect our rights to the resources in our territory. The government must allow only the entry of the citizens and people they have deemed fit to enter. If the government allows anyone to enter without proper vetting it breaches its contract become worthless. One should start asking ones self if it is worth the dues being paid to the club.
With an estimated of 20 to 30 million aliens in the country the government has clearly failed to meet its obligations to its citizens. The only question now is, what will the citizens do about it?