USA, of course is a very highly developed and advanced country but developed country is defined on many parameters and in many of those parameters USA is not on the top. What you probably meant to say is it being the largest economy in the world and yes it is the world’s largest economy as of Dec 2016. At this point US is still considered a developed country. In fact the definition itself was based on US to begin with. US had major advantages after WW2 that they utilized very well for development but as others are catching up US seems to be falling behind in most areas.
