Death by taxes.
Here’s the thing. You have a decent idea for an ice cream and coffee shop operation in Mainz, Germany. You, the American, have your own cash and willing desire to put up a four of these ice cream shops that might draw $150,000 a year in profit revenue. Once you arrive and start to establish everything....then you want to open up a bank account and do regular German business, and the German banks (not all of them but the bulk of them will say this)....”No thanks”.
With the US banking rules in place....it is a royal pain for any German bank to deal with an American citizen...especially who makes profits and tidy incomes.
If you were Mexican, Cuban, or Honduran? No problem.
Yep, the US government finally created a law that limits your business capability, your risk-taking, and your capitalistic dreams.