Of Tolkien and Eagles

Question: What is it with Professor Tolkien and eagles.It seems that evrytime someone in one of his tales has to face a rather hopeless situation , BAM, an eagle or eagles show up to save the day. Case points when in the Hobbit the group are surrounded by wolves  eagles show up to save the day, when Gandalf is stranded on top of Sarumans tower who shows up to fly him away, when they are battling in front of Mordors gate who shows up to aid them and then flies off to rescue Frodo and Sam, who else but the eagles. It seems to me he badly overworked this particular rescue scenario. Also, whom did the Eagles represent? America? I'm not sure if that is so but the English at that time were depending on America to see them through WWII. Just a question which maybe has no answer but an interesting one to me, I wonder if anyone else ever pondered this question. Oh well good bye for now and hoping that you get all that you wish for and maybe a little more.