I would suggest that it is not so much about being Mr Nice Guy as it is about FEAR OF THE US DOLLAR NO LONGER BEING THE GLOBAL RESERVE CURRENCY. In other words, it is more about protecting the US Federal Reserve System. The more the dollar is spread globally, the greater its recognition. So it is a sales operation.
There are two problems. 1. The greater the availabity, the less the value. But more importantly, 2. Open Borders is contrary to any concept of nationalism that protects its citizens, which in turn not only destroys the need for a national government, but also makes national GDP meaningless, which in turn impacts a currency’s value negatively.