I suspect that since there is apparently no dictionary entry for the word you're asking for, the very concept is nonexistent, or, a fable.
The best you will probably find is something that could originate from Mao's Little Red Book:
"Running dog of the Imperialist US Lackeys"
I'm sure Stephen Colbert would heartily concur.
Edited to add:
@FumbleFingers has suggested that this answer seems more like a flippant comment than a real answer, and indeed he may have a point. But I do recognize that the question was asked in all seriousness, and my actual serious answer is contained in my first sentence. In other words, despite the proposed candidates, such as Americanophile, there really is no such word.
The remainder of my original answer above was editorial comment. I've been around the block, and lived in a number of countries, and I have loved them all. Having lived in all three countries for years, I am an Anglophile a Germanophile, and a Canadophile. From this residence experience I recognize that there is a certain degree of awe or even fear of the United States, as the foremost economic and military power of the past century -- although this is expressed more often as affected disdain. What far too few seem to recognize, however, is that the modern power of the US is rooted in its diversity, and expressed in its union. "E Pluribus Unun" = "Out of Many, One". To be Americanophile is to combine Anglophile, Germanophile, Hindiphile, Latinophile, Francophile, Sinophile, Russophile, Italophile, Poliphile, Afrophile, and many more. In short, the United States is in effect The World Country. There is no country nor culture not represented here, and the larger the diversity the stronger we are -- as long as we are united. May that ever be so.
But that won't stop the Colberts and the other self-loathers from putting down what should be admired and even loved, even by those outside the US.
I apologize if this seems excessively patriotic. This isn't my intent. My intent is to show that if there is any greatness in the United States, it is great because it is the World united in one.
Hence there cannot be a genuine word such as Americanophile.
PS: Yes, I know that the original intent of "E Pluribus Unum" was "out of many states, one country", but I submit that we've evolved well past that original meaning.