So was the Iron Curtain. Arguments like that don't necessarily keep governments from embarking on foolish projects. Sustainability in this case also is a quest

So was the Iron Curtain. Arguments like that don't necessarily keep governments from embarking on foolish projects. Sustainability in this case also is a question of scale and the particular design and purpose. Both Hadrian's Wall and the Limes lasted for quite some time. Misguided and malevolent as the intent behind that wall may be if completed it quite likely will contribute to keeping people out of the US just as much as the Iron Curtain for some time was a mostly effective tool for keeping people inside certain countries. So, is that wall desirable? No. Is it sustainable? That depends entirely on what resources the American people are willing to commit on its long-term upkeep. Either way, building and maintaining such a wall is a colossal folly because the funds required to do so will of course be lacking for other, probably more beneficial projects. Unfortunately, that doesn't necessarily mean it isn't happening.