From an artistic standpoint, there is an argument to be made for the ambiguity. Whether or not they MEANT it as a threat, I can't say, but judging from the "and will be again," in the second quote -- it certainly sounds somewhat threatening. That, however, makes the ambiguity argument no less logical, particularly from an artistic standpoint.
I just hate any and all divisive identity politics -- and this certainly falls in that category.
Second, I agree: the only identity politics we should have here is as Americans. What the artist did was divisive and anti-American, and from the sound of her response, she knows it.