I think doing as well as NZ would be a laudable goal. If the whole world did that well, then I think COVID would be quickly eradicated.

But, beyond the fact that the US has large land borders, the US has a genuine problem. We are economically dependent on legal and illegal cross-border seasonal migration. I personally think that, with actual political will, the borders could be made a lot less porous, but this would involve attacking the supply and demand sides. Neither party is interested.