It is awkward, I get it. Our country has a long name which is also the name of a Continent (or 2 or 3 depending on your views...I like to think of us as one).
Actually I learned that the US were not the only Americans and it hurts people's feelings that we think that when I lived in South America....I wish I had come up with it on my own, but as a small child in Argentina I was constantly reminded that the entire continent is America and it is arrogant etc to call ourselves Americans.
Now what to call ourselves? It is awkward....we watched a WWII movie this weekend, and it was the British, the Japanese, the Canadians and the American's. The soldiers from the USA does seem awkward when everyone else has nice short names....and I totally get that for many people Yanks is derogatory (not for me, I could care less personally)
Maybe we say American because it's easiest?
I do try to make a point of saying US and USA when I can and wonder in what other ways I can be respectful to the fact that the US is not the only America.