not sure I'm following you.  haven't you answered your own question.  the immigrants are coming for jobs and economic reasons, but likely also for a mixture of other things like safety, upward mobility, freedoms of many kinds.

there are jobs, and if the immigrants were kept out, it would be harder to fill those jobs, so either the wages would go up, or the jobs would be automated, or shipped outside the country--probably some of each.

The immigrants fill those jobs for lower wages, and if they are illegal the employer can usually save on social security contributions as well. By increasing the supply of work at lower cost, the immigrants hurt the domestic workers, but if the immigrants were not there not all their jobs would be filled: each worker would be more costly and so fewer would be hired. So, if you had as many illegal immigrants as unemployed citizens, removing the immigrants would not reduce the unemployment to zero. Far from it, actually.

guaranteed to evoke a violent reaction from police is to challenge their right to "define the situation." --- David Graeber citing Marc Cooper