I don't think it's very applicable to think about this news as taking away from anything they could do in the US Parks. Disney is not financing this, imagineering is just contracted to build it. But it doesn't have to take away from future expansion in the US--that would or would not happen regardless of Abu Dhabi. Imagineering built Epcot at the same time as Tokyo
Disneyland. These are separate things.
ETA: the influx of cash might also help in paying off Disney debt from IP acquisitions, which could indirectly benefit us Parks and consumers