Adding text to title of posts when combining RSS feeds

Hi,
I have two INPUT rss feeds:
(1) https://feeds.bbci.co.uk/news/world/us_and_canada/rss.xml
(2) https://feeds.bbci.co.uk/news/world/middle_east/rss.xml

I want to combine the two rss feeds into a new rss: “NEW_RSS”.

However, I want the titles of each of the posts/items of the NEW_RSS feed to begining with
– “US :” followed by the input titles for the stories that come from feed (1) and
– “ME :” followed by the input titles for the stories that come from feed (2).

Is there a processor that does that?

Thanks