The relationship between France and the US is complicated to say the least, I'm not sure if "allies" is a term I'd use at all anymore. We are however the primary market for video games right now, and this is one time period we clearly remember being allied, and it exists as a subtle reminder of French intervention then. Assuming there was any nationalistic consideration her at all, as opposed to simply deciding American patriotism sells to Americans.
Freemasons having a substantial prescence in the US is very true, there has been a lot said about it over the years. Indeed it's arguably the reason why we had the awkwardly stated "freedom of religion" in the US, rathe than simply specifying Christianity which was the actual practice. The Freemasons still being pseudo-secret.
I could see this going a number of ways to be honest, in part I suspect that this might be a veiled way of justifying putting the gory murder of both American and British historical personages into the game which would kind of play havoc with the bit about marketing above.
Where this goes remains to be seen, I don't know anything, I could see it going in a few differant directions. Overall though two things can be said about this:
#1: The typical "Assasin's Creed" apperance doesn't work. It could be argued that the cloaked pseudo-hoodie look could fit in either in the middle ages or to an extent in the renaissance where I think it was pushing it for "indiscrete" since having your hood up that much would have been unusual in some of those enviroments. It doesn't fit at all in the late 1700s, France might want to look at some period costumes.
Basically going by that artwork if we're to assume our assasin is going to blind into the streets of say 1775 Boston by putting a bright white hood up over his head and walking slowly, that is going to be comedy gold. For this reason I'd almost suspect this cover has to be a phrank... I mean seriously think about it, yet it hides the face, but this does not scream "stealth" or "assasin" which is kind of the point of the series.
#2: To be honest, I sort of feel like Ubisoft is out of ideas here, and has been stealing from their own imitators. This seem similar (by no means identifical in setting) to the game "Backstab" which was an iPhone/Kindlefire/Pad/whatever game going for a vibe similar to Assasin's creed where you basically took out old world soldiers with now antiquidated firearms using a lot of the same kind of gameplay you'd have expected from Assasin's Creed. I've never bought it, but I've seem it, and have heard some people claim that while simplified they actually thought it wound up being better than AC. I think the game was by a company called "Gameloft" or something like that, the guys who did a scaled-down version of WoW as a full featured MMO for portables (Order and Chaos I think it's called).
It's not a terrible idea in of itself, but it makes me think they are imitating their imitators.
As a series I don't think Assasin's Creed ever had a planned ending to be honest, the nature of the franchise lets them drag it out for as many installments as they happen to want. I don't imagine we'll see an ending until we see some serious flagging from one or two of the chapters at which point they will try and get one more burst of sales with a finale and worry about tying it up at that point.
When they DO tie up the series, I suspect it will be with one final mind trip where your going to have a descendant of Desmond (as opposed to Desmond) doing his thing against the organization(s) toying with Desmond. We'll probably find out that the oftentimes awkward and disjointed narrative (the desmond sequences being criticized) is now justified by the "reveal" that it was someone remembering desmond being forced to remember.
It's possible that the finale might also be a situation where whomever is "remembering" desmond doing his remembering is using new technology breaking the rules set from the tech used on Desmond due to it being newer, in order to stop some kind of super assasin created with his combined knowlege, all of this knowlege being used to grant parity or something.
It's just a thought, but it seems like the obvious "surprise" in a series this heavily based on mentality. The idea of the dreamer themself turning out to be a dream so to speak. Given that Ubisoft to me seem to be running low on ideas for this franchise... well a few years down the road, remember I called it here.