To try and untangle a bit, based on my own experiences and training as i worked for a Japanese company for several years...
Japanese see 'being Japanese' as being part of a race. You're born in to it, They are very proud and conservative in this view or Japanese identity. One can sort of 'convert', which is different that becoming a citizen of Japan and no-one i know of Japanese birth really would talk about 'converting' in this way, and it still wouldn't make someone truly Japanese in their eyes.
America is an Ideal (at least used to be, that is perhaps questionable at this moment), based on and espoused by the beliefs of Liberty articulated in the Declaration of Independence, US Constitution and BOR, and the underlying tenants of Natural Law. We are a sovereign Country but Not a Race (in traditional definition). Our identity is (used to be) based solely on these beliefs and the XIV amendment enshrines this when it says "Those born or naturalized...." Divided loyalties is a real issue and other parts of the Constitution (inclusive of amendments) acknowledge the concerns but only in placing limits on Representatives, Senators President & VP...
I get the metaphor 'Climbsinsink' was building, but there are real differences between US and Japan so it doesn't really work.
Dinesh D'Souza is an American once he declared his belief and support of Liberty and became a naturalized citizen. That doesn't mean everyone needs to fully trust in him, but i think he has consistently espoused these values in his works.
Lastly, there are plenty of others who take the steps of becoming a citizen in name only but clearly do not understand or espouse Liberty in the American definition and ideal...
Let's save our critique for them!