So by what criteria is Britain not "a stauncher ally"?
I didn't write that. My point was that a strong friend or ally is a friend or ally who is strong, whereas a group of persons with whom someone has a strong friendship and alliance is a good friend and a staunch ally.
So this was what Obama wanted to say: France is not stronger than Britain, but it is now, other than some years ago, as reliable an ally as Britain has been for a long time.
Actually both Sarkozy and Obama have changed their countries' foreign politics substantially.
Now my own opinion:
Countries cannot be friends, governments can (to some extent, and subject to revocation). Countries don't start wars, persons in power do, and soldiers have to fight them, more or less enthusiastically. If you are lucky, you can elect your government according to your interests, but you should never let them govern your emotions, or you are on the losing side even if your government wins.