I don't know why some experts think that it 'could have helped ties' (and this forum is not the place to discuss the possible reasons), but there are (at least -it's not a model of clarity two possibilities:
- the war in Iraq actually, maybe, helped Anglo-French relations
- the war in Iraq, if handled differently, could have (but didn't) helped Anglo-French relations
Fuller context might make this clear.
Student or Learner