4.5 month visit visa for American

Thanks for all the tips and advice.
I'm beginning to regret booking such a long trip...my friend told me I could stay up to 6 months, and while that appears to be technically true, I wasn't considering all the extra hassle a long stay would mean at immegration 

You should be fine, given your ties to the US and the documentation you'll be bringing - as others have said. 9 times out of 10 someone in your situation will probably have no issues whatsoever, it just helps to be prepared for that one IO who may grill you.

As someone who was recently in line behind an unfortunate girl who was staying in the UK for a few months, believe what you read here....you really need to have your ducks in a row when coming through the border. Although it is true you do not need to apply for a visa in advance, if you are staying more than a few weeks typical touristy length of time, you REALLY need to have the other info mentioned. It sounds like you have all that so you should be good :-)

The girl in front of me when I arrived here in Jan had no paperwork to back up her story of just "visiting friends" for a few months and they were not buying it. From what I overheard she could not produce a letter from the people she was staying with and the poor girl seemed pretty clueless about the process. She probably thought she could just come on in, lol. I do not know the overall outcome for her, but she was taken aside by other officers while I was still in line and it did not look good.

I hope you enjoy your stay and if you have the appropriate documentation, and it sounds like you do, then it should be all good for you :-)

IMO, the letter shouldn't come from your friend, but from the family member(s) who own the hotel.  Your friend doesnt really have the right to say if you can stay there free of charge unless she runs/owns the hotel.

One additional thing, maybe you already have it in your letter, but if not, make sure that you are carrying contact numbers for your friend's family where you will be staying, and that they know approximately when you will be arriving so that they can have their mobile phones on, just in case an IO wants to independently confirm what you have told them.