How should I position myself in the US job market if I am an assistant professor with tenure? In my country, job rank is not aligned to tenure. You can be an Assistant Professor with tenure (i.e. a permanent contract at the university) or without tenure (on a temporary e.g. 5 year contract), or you could be an Associate Professor with or without tenure. I have tenure, but I am an Assistant Professor... which I understand is fairly rare in the US (if not non-existent)

If the time comes that I want to look for a position in the US, I assume based on the feedback from my previous question that I should focus my search on an Assistant Professor position rather than an Associate Professor level position.

If I were to apply for an academic position in the US, how should I explain this? Is it worthwhile to mention that I have tenure already? Do I need to ask for a shortened tenure clock or will it be decided by the university on their own?
They will not care about your position outside US. They will care about your publication list mostly. There are countries where people get a formally permanent university position just after PhD, but their are not called professors immediately. This fact does not, however, mean that their position is equivalent to the tenured professor in US.