> Why would the US and EU losing manufacturing be bad?
Because if they can't make thing you can win a war - just stop all their trade and then invade. When they are limited to stick and stone while you have guns war is easy to win.
Of course in reality the US and EU are not in danger of losing all manufacturing, and their military leaders are will aware of this and so put extra effort into keeping some important manufacturing in the country. Politicians are generally (but not always!) aware of this and try to be friends with others who can make things you don't make locally.
Because if they can't make thing you can win a war - just stop all their trade and then invade. When they are limited to stick and stone while you have guns war is easy to win.
Of course in reality the US and EU are not in danger of losing all manufacturing, and their military leaders are will aware of this and so put extra effort into keeping some important manufacturing in the country. Politicians are generally (but not always!) aware of this and try to be friends with others who can make things you don't make locally.