You really think all those manufacturing jobs were low age? Even if they were, how exactly does shipping all production and jobs overseas to allow the top 0.1%/MNCs in the US have a higher profit margin help the economy in aggregate or even the US Government? All it does is move the tax base (and hence, tax income) overseas and allow MNCs to destroy small and medium size firms in the US that operate in the US and pay a higher tax rate.
In the long term, military power is proportional to economic power (i.e. aggregate GDP). Therefore in order to protect the constitution and the USA I want the aggregate economy to grow.
I also believe labor specialization has been one of the most important factors in global and US economic growth. Why should I care if my TV is made in Korea or Kansas? The people of Kansas have other things they make.