If interests of one region buy up all the production of another, they inevitably move all production to one place, their original base. Ports, mines and railways are a generally an exception to a the rule, but still lots of positions on management, engineering, logistics etc are lost in the selling country/region and moved to the buying one.

To elaborate on the US-EU analogy:

In US, some regions concentrate more wealth and power than others, having the majority of production and/or headquarters based there. But in the US there's real freedom of movement. You can work in Montana one day, move to Florida the next, and it's no big deal. The residents of economically disadvantaged areas have to carry the burden of moving away for work, but that's the only burden they face.

In the EU there are 24 official languages. Simply put, you can't just move anywhere you'd like to be. Learning a new language takes many years. I've been using English almost daily for 10+ years and I still come across new words quite often. Primarily due to this reason, in the EU, freedom of movement is allowed only on paper. Workers from disadvantaged areas have to take on a huge burden if they decide to move. They have to learn a new language, a new tax system, a new everything from workplace H&S rules to mains outlet types. Also they often face a lot of discrimination (even if language skills aren't a dead giveaway, ethnic differences are usually visible to us, even if they would seem minute to an American). So essentially when a factory moves from Italy or Slovenia to Germany, the locals lose a lot more than just the inconvenience of having to move across a couple states for work.