I know Cambodian Cuisine closed a few years ago (saddest story ever behind that..) and Kampuchea is definitively nothing like Cambodian food. Southeast asian food in general seems to be a tough find in the NYC area... any suggestions?
Not to be pedantic, but it depends on how you define Southeast Asian. The main SE cuisines that are virtually or totally missing from NYC are Cambodian, as you noted, and Lao and Burmese. Of those, the best you used to be able to do was indulge in the Isaan Thai menu at the incredible Poodam's, which has tragically shuttered; Isaan Thai food is cognate with Lao food. (Has anyone tried the Thai restaurant that supplanted Poodam's?) Zabb Thai purports to serve some Isaan food, but I heard that closed too -- not sure -- and anyway, while it was very good I didn't think it held a candle to Poodam's. Ayuda, which is amazing, is going strong and will make you a bonafide Isaan som tam and other Lao-style dishes.
Cambodian and Burmese food are even less frequently and well-represented here. This is a tragedy, although it should be noted that these are the region's weakest cuisines. That is comparatively speaking against a rather high bar -- Thai, Vietnamese, Indonesian and the island melange cuisines -- but still, it's probably not for nothing in explaining, along with immigration patterns, why we don't have more Cambodian and Burmese restaurants.
I beg to differ on Cambodian being a weak cuisine. In spicing, variety, and subtlety it is the equal of Vietnamese, at least as I have experienced each of the cuisines in restaurants run by people from those countries in the US. Have a look at "The Elephant Walk Cookbook", the recipes are exciting and produce extremely good food. I wish there were a really top-class Cambodian restaurant in NYC.
I agree that Cambodian is not a weak cuisine; I wrote that it and Burmese are the region's -- mainlaind Southeast Asia's -- weakest cuisines. That's a really high bar. Objectively, Cambodian and Burmese foods are wonderful.
I've found this to be the consensus among non-native Southeast Asian food lovers who have been to the region. (I mention them as my sample, because natives work within a distorting framework of national bias.) I've been there too, though not to Burma. Your impression appears to be based on the American versions of Cambodian and Vietnamese food, and it is accurate for those variants. I love that you alluded to Elephant Walk, which when I lived in the Boston area well over a decade ago was a delightful restaurant. By and large, Vietnamese food in Vietnam simply blows away American Vietnamese food. There really isn't a comparison. Alternately, Cambodian food in America, when done well, tends to blow away its antecedent in the motherland, at least the version you get in Phnom Penh. That's because even now Cambodia hasn't really recovered from the genocide years; it's squalid and there isn't a lot of time and money to knit together dazzling displays of leisure culture, including food. (For the sake of perspective, note there can also be parity -- for example, some Thai/Isaan restaurants in Queens, NY are of equivalent quality to very good restaurants in Bangkok.)
So, in America, the way this works out is good Cambodian and Vietnamese are about on par with each other. In mainland Southeast Asia, for my money Vietnamese is actually THE BEST of them all, in spite of what people say about Thailand and Laos. Two of the reasons Vietnamese is so much better in Vietnam are American Vietnamese tends to emulate a narrow subset of the overall cuisine, whose flavors are sweeter and comparatively insipid; and the cuisine is based heavily on local fruits, vegetables and herbs that aren't exported as freshly or at all.