How do you explain some americans fears over the international trade agreement

American fear that an international trade agreement will always result in them been left behind as it allows easy trading between America and other country which is seen to affect America's ability to self produce, triggering a reduction in industrialisation coupled with losses of jobs. The believe is that allowing foreign trade brings in foreign companies to either come in and set up their own company (creating job competition between Americans and foreigners) or total dependence on supply of externally manufactured goods and services.