Actually, you can delete and attempt to rematch files, sometimes to great success.
But first you must recognize that songs are often available in different masterings, so an old copy of The White Album might not match to the 2009 masters that are in the store. Also, albums that are reissued by different labels, vendors, or with minor changes to the files that were provided to iTunes (for example, when two tracks that flow together are split at a slightly different index) won't match properly.
If you are reasonably sure that the album you are trying to match is the exact album, then this is generally how it goes:
1. Match the album. Occasionally a track or two will upload inexplicably, while the rest will match.
2. Make sure the files you have (or that you just ripped from CD) are stored somewhere other than your iTunes folder, so when you delete them from your library, they will not get trashed.
3. Delete the cloud version of the file in question that shows as "uploaded." That track should now be missing from your cloud library altogether.
4. Add the file from your hard drive again.
5. Convert the file to a different format, such as WAV or MP3 (if the original was an AAC). Delete the one that you have stored elsewhere before the match mechanism runs, but leave the newly converted version.
6. Run the match mechanism again. Most of the time this will show the file as "removed." After this has happened, run the match mechanism AGAIN.
Depending on the file, you may get yet another upload, or miraculously you might get a match. I'd say 70% of the time it will just upload again, and that can be undesirable as it is now uploading a file that is not the format you wanted to upload. If that's the case and you have nothing better to do, you can delete the upload and rerun match on the original file again, twice (once getting the "removed" result and the next another upload).
RTW