Historically many American cryptographers worked for the NSA, of course they are not going to disclose it. Maybe a group of them did create Bitcoin. Does it matter? Not in the least, because its Free Open Source Software. The NSA made SELinux in a hope to better secure assets from other agencies, and yet anyone can benefit from that project.
Replacing the US Dollar may be harder to justify for a State entity, but its true that people working there have the passion for it. I wouldn't be surprised, nor care if it was a direct project, or indirect project. Didn't we have Tor from the US Navy? Who else used Tor?, yeah, Satoshi connecting to this forum of his... Same story, FOSS use it if it benefits, check the code if you are paranoid of backdoors.
TL;DR: Who cares. Good for them if they did.
It does matter as to who owns the more than a million coins owned by Satoshi. Whoever is the richest matters especially now that BTC is becoming more accepted even by the countries that don't normally accept it.
BTC will not be created by someone/group who will not benefit from it as well. And if it's created by NSA cryptographers then BTC's existence didn't just happen in a vacuum.
