Sorry, but I see nothing in your xml file that would allow darktable (or any other program) to reconstruct the tag tree. So all it can do is assign each tag or its own. (not even uppercase initial letters help, as you have geographical names as subtags).
As an aside: if you don’t export the parent tags as part of the tags for each image, you will end up with a much larger number of tag trees. Perhaps not what you want.
If possible, re-exporting the sidecars from lightroom with hierarchical tags is probably the easiest.
If not possible, you may have to correct the tagging “by hand”. Fastidious, but not impossible if you have the tag structure in place: select all images with tag “tortilla” and assign “Food|tortilla” to them, then remove the tag “tortilla”. At the end, remove tags with 0 (zero) images.