The web application or web site at http://domainame could not be found. Please
create web application and web site in http://domainame and then click “Retry”. Click ” Cancel” to abort setup
FIM Portal and Service is trying to find a site which is not there anymore. Just add the url which FIM was looking into the Central Administration >> Alternate Access Mappings
Save and exit out from Central Administration and try to uninstall now and it should work. It worked for me.
Aryan Nava 