I’d give the nod to Tim, because I don’t imagine that anti-immigration activists are going to be bought off so easily. Instead, a permanent, multi-generational class of non-citizens would just be fuel for the fire. Twenty years on, immigration foes will look at all the second- and third-generation non-citizens we’ve created, and the mass arrests and deportations will really begin in earnest. Not a problem I’d want to create.
Worse, by then the anti- side may even have a point. A permanently alienated underclass isn’t going to be so loyal or so invested in the American polity. They wouldn’t have any reason or need to be. The genius of birthright citizenship is that it changes the incentives for everyone involved. It says to all populations: You’ve got roughly twenty years to figure out how to live with one another, as citizens. Now get to work.
Seems like it shouldn’t be an impossible task.