In our XML site map, we inadvertently used a URL that:
1. Was a 301 redirect.
2. Was slightly different than the canonical URL for that page.
3. Was different than the URL used in our HTML sitemap. The one used in the HTML sitemap was the correct (canonical) URL.
The difference looked something like this:
XML Sitemap URL: domain.com/keyword/CA/Los-Angeles
Canonical and HTML Sitemap URL: domain.com/keyword/California/Los-Angeles
When visiting the /CA/Los-Angeles URL you are 301 redirected to /California/Los-Angeles.
This error was hidden in plain sight for a couple of months until we realized what we had done. We have performed miserably in search results for long tail keywords that included city/state (that we used to dominate) since this mistake happened.
Is it possible that this simple discrepancy could be the primary reason for this fall in rankings?