Again money, stocks, and bonds are not capital. Capital is name for things that capitalists have invested in in order to make and sell commodities for profit.
Financial Capital is not capital. It is not even paper. Its speculation and rent.
Saudi Arabia sells oil to america but the Saudis can't buy whatever they want. Their money has to stay in america. They only get to buy enough american military equipment to keep their neighbors from invading and their people from revolting. The rest they have to spend on stocks (but never controlling interest.) They aren't even allowed to buy gold bullion. Their finance "capital" is only able to produce more "capital" and nothing else. If they can't use it for anything else it is worthless.
You can't "just sell" stocks, there has to be someone to buy them (and they'll get them cheap). Regardless of who owns the stocks or what they are valued at there is capital in europe and that capital has productive capacity. The owners will want that capital, whether it is factories or farmland or data centers, to work at capacity to generate maximum profit. Being subject to the whims of empire is the primary impediment to profits.
Sucking stock value from europe and injecting it into america will not make america produce more. The factories will stay in europe. All the process will accomplish is putting the economic leverage in the hands of european capitalists who are willing to stand up to the american empire.