The effect of weakening the dollar is not to return manufacturing jobs to the US while allowing the same dollars to buy the same products. It's to make imported goods more expensive so domestically produced ones win out in the marketplace, both in and outside of the US. To make you switch because your favorite products become too expensive.
It's to make you chose Californian wine over French one, so to speak. Whether you are in the US or elsewhere.
If technological advancement is going to kill the working class, this might slightly accelerate that development but it does not change it one way or the other.
