I interpret it as pointing out that it's early days in her vice-presidency and with Covid making travel more difficult as well, so she hasn't yet traveled to places that you'd expect her to visit as a VP, both the border and Europe. But it's not a very convincing reply, no.

Although since you mention it, it's true that the illegal immigration problem is broader than just people illegally crossing the border - for all the people who just overstay their visa, whether they're European or Latin-American, the US-Mexican border is irrelevant. And even for those who do come across the US-Mexican border, I do think it's more important for Harris to visit their countries of origin as she is doing, than to visit the border.