> For manual labor there's no amount of money you could pay Americans to be farmworkers.
If you don't think Americans are willing to pick fruits and vegetables, go find a farmer, have him put a sign at the edge of his property that says "Free fruits and vegetables, you pick them yourself" and watch how quickly the field is emptied.
This is obnoxious pedantry which is ignoring the parent's obvious actual point: food obeys a demand curve just like every other product, and what the parent clearly meant was that, at the labor price native Americans would want for these jobs, the resulting food price would be such that not enough people would buy the food to make it worthwhile.
And while this may have been idle speculation a few years ago, we now have pretty solid empirical evidence: when food prices increased by 10-20%, even in the middle of the fastest-growing wages in decades, the country had a collective temper tantrum.
If you don't think Americans are willing to pick fruits and vegetables, go find a farmer, have him put a sign at the edge of his property that says "Free fruits and vegetables, you pick them yourself" and watch how quickly the field is emptied.