The conference committee adjusting House-Senate differences on the immigration bill not only has a political problem in the United States; it has an international problem in US relations with Mexico. This international problem is a classic illustration of Mexican ambivalence toward the US.
Mexicans are terrified that the US will take effective steps to control immigration. This would close the safety valve which for years has released social pressures in Mexico. With the valve closed, the pressures would increase to the point of threatening the established order. The pressures could be contained in other ways, of course - such as genuinely reforming the Mexican economic system so as to give the little guy a break - but the Mexican establishment doesn't want to do this. The establishment benefits too much from the status quo.
The Mexican government has become so accustomed to the present system that it takes it almost as an affront that the United States would seek to change it. The Mexican Constitution guarantees the right to leave the country, and Mexicans sometimes sound as though this includes the right to enter another country. At the very least, the Mexican argument runs, any change should be worked out in discussions between the US and Mexico.
Mexicans are somewhat ashamed that so many of their countrymen are forced to seek a meager livelihood in a foreign land. This is taken as a reflection on Mexico's ability to provide for its own people.
Mexican pride is further offended by the perception - probably exaggerated but with a basis in fact - that Mexicans, especially illegal immigrants, are mistreated in the US. This mistreatment ranges from reports of brutality by the Border Patrol to exploitation by unscrupulous employers. It must also be admitted that, especially in the Southwest, there is a residue of racial prejudice among Anglo-Americans.
Finally, Mexicans are uncomfortable with a situation in which so many people who cannot make a living in Mexico are able to scratch one out in the US only by working at menial, backbreaking jobs that Americans don't want.
This last is one of the points at which the domestic and international politics of the immigration bill come together. The House added an ill-advised amendment to the bill under which temporary foreign workers, the overwhelming majority of them Mexicans, may be brought into the US for seasonal work. The bill puts no limit on the number of such workers, and some experts think it might reach 500,000 a year.
The argument for the amendment is that most of the workers who now harvest fruits and vegetables are in the US illegally and that, with the amnesty provided by another section of the bill, they will leave to seek easier jobs in cities. (A different section of the bill would fine employers for hiring other illegals.)
The argument against the amendment is that the growers could hire Americans if they made the jobs more attractive. Failing this, the amendment is an admission that the US cannot harvest its own crops. That is another way of saying that the US cannot feed itself - an embarrassing admission for a country which brags about its productive agriculture.
There's more, and it gets worse. The temporary worker amendment is also saying to the Mexicans: ''We don't want you to come to the United States to live , and we'll keep you out if we can catch you; but you're welcome to come for long enough to put fruits and vegetables on our tables.''
What is proposed in the House bill is the creation of a permanent underclass whose presence would be tolerated only for the few weeks or months it is useful to us and for whom we would assume no responsibility the rest of the year. Rep. Henry B. Gonzalez (D) of Texas aptly called this program ''rent-a-slave.''
The problem of illegal immigration embraces so many related issues that the bill now before the conference committee is unavoidably a fragile tissue of compromises. Interest groups offended by one provision are placated by another. The bill's chief architects, Sen. Alan K. Simpson (R) of Wyoming and Rep. Romano L. Mazzoli (D) of Kentucky, are to be commended for what they have accomplished. Their bill ought to be passed.
But neither Simpson nor Mazzoli designed a temporary-worker program. This was added on the House floor as a sop for agribusiness.
Pat M. Holt, formerly chief of staff of the Senate Foreign Relations Committee, writes on foreign affairs from Washington.