How does buying assets change net capital outflow?
Net capital outflows from the US would increase. Net capital inflows for the foreign country (investment) would increase. This keeps the accounting equation equal. For the US S-I would increase, thus creating a balance of trade surpluse (even though these are financial assets). For the country receiving the inflow S-I (savings-investment) would decrease, increasing their deficit (assuming the balance of trade began equal). This balances both sides of the trade. Our net capital outflows grow by an equal amount to their net capital inflows in this situation.