>Farm labourers became unemployed as a result of govt. policy to undermine farm worker political power.

No, in the last 2 centuries we have simple automated the vast majority of farm labor.

>More labour intensive farming would be a good thing. At the moment the US uses 10cals of energy to produce 1cal of food. Pre "get big or get out" it was 1 in 2 out.

This is an entirely meaningless metric.

>Back to manufacturing, it is free trade that has gutted US manufacturing capability.

Yes but my point was that banning automation would be more effective at creating jobs than banning trade. They are economically equivalent. A port is essentially a machine that produces stuff with less (local) labor.