In Canada we call that type of work 'essential workers'.You know illegal immigrants don't hold green card and doesn't pay taxes right? they mostly get paid in cash (convenience of cheap labor) so what do they really contribute? "picking vegetables and fruits" is not an excuse. they also put a strain on hospital and social services including law enforcement. at the end of the day, government services for citizens shouldn't cover them but they still benefit off it...
US capitalism can't function without the cheaper labour of illegal immigrants.