There are half a billion people in the USA; there are 20 million in Australia. Thus, the USA needs many more agricultural workers.
And it has more people who could fill those jobs! Funny how that works, isn't it?
You could get rid of the illegal agricultural labor in the USA, you just would no longer have any fruits or vegetables.
I wonder how much fruit prices would go up if we were to pay the pickers a fair first-world wage. Let's do some maths!
If I buy an apple it costs about $1.60 per lb. That includes the picker's labour, plus the costs of land, pest control, irrigation, transport, the farmer's profit, the retailer's profit, the middleman's profit, and the little sticker that tells me what kind of apple it is.
According to this Canadian site: http://www.bctree.com/orchards/picking.php it looks like an inexperienced picker up there makes about eight bucks an hour, getting paid to fill 800-lb bins at $15.60 per bin. Quick sanity check: that's three pounds of apples per minute, an apple weighs about a third of a pound, so that's nine apples every minute on average. Sounds like a plausible sort of rate.
So if pickers are only getting $15.60 for an 800 lb bin, that means that the cost of picking is a mere two cents per pound, for apples that retail for $1.60/lb! So if we were suddenly forced to pay apple pickers $32 an hour instead of $8 an hour it would raise the cost of our apples from $1.60 to $1.66. Or, like, two cents per apple.
Hardly sounds like an unreasonable price increase to me.
So in conclusion, I think anyone who is claiming that decent wages for farm workers would make agriculture impossible is off their fricking rocker.