I've lived in the Netherlands for a study abroad and in Vietnam. The study abroad was cool, though with classes and the living arrangement I didn't really get into the culture much. It didn't seem terribly dissimilar from the US on any level I saw, but I was only there for a semester. And I lived in a castle, so not really a good "everyman" experience.
Prior to living in Vietnam I basically knew that in the US they sold phở and ran nail salons. Of course I knew about the Vietnam war and a little about Ho Chi Minh. But no, no language to speak of. After college I got a TEFL certificate and a job offer in Vietnam for a position at a well-known (and often derided by ex-employees) English school in a small city where most of the oil production is done. Oil=international business and a whole lot of peripheral business to cater to the guys working on the rigs, so it's a bit bizarre. In some ways HCMC/Sài Gòn is no better, but it's different.
The thing about Vietnam and its people is that they have a very, very strong idea of who they are as a nation and though the South hates the North and the middle of Vietnam, based around the old imperial capital of Huế has its own identity, as does the Mekong delta region, all essentially agree that they are one people. The reason Nguyễn is such a common surname is that it's the only Vietnamese family name that does not have a Chinese origin. Furthermore, most of the people belong to the ethnic group called the Kinh. Add the natural border of essentially impassable mountains that separates Laos and Cambodia, save a few tightly controlled passes and you've got a good setting for some serious unity.
That said, an outsider can never be Vietnamese. Even war babies are not considered truly Viet, though children from the American War as they call it, can gain citizenship after going through a really Byzantine process that involves never setting foot outside of the country for a 5 year period. If they were born in the country, they technically have citizenship but are generally looked down on. This also goes for Việt Kiều or overseas Vietnamese. These are often looked down on because they fled the war and are now returning to buy up land and businesses and generally be kind of shitty. As for those that served in the South Vietnamese army, they were stripped of citizenship and papers and so could not be a part of society except for motorcycle taxi (xe ôm) drivers or cyclo drivers and things of that nature. I once rode with one of these guys and it turned out that he had been a radar operator at a U.S. run base and for the last few decades has been scraping by. I would have doubted it, as many have sob stories but he said it in impeccable English, which is hard to come by in Vietnam. South East Asians in general, excluding the island nations have the toughest time picking up natural sounding accents because of the grammatical structure and the phonemic palette used in the languages.
So to loop back to culture, many Vietnamese do not understand how being American works. I can't tell you how many thousands of times I had to explain that my parents are immigrants, that I was born here and that I am in fact just as much an American as my blond-haired, blue-eyed, corn-fed friend. This attitude, coupled with unscrupulous business practices by many foreign companies when Vietnam re-opened to trade in 1991 as well as the deep distrust the Vietnamese have historically held against foreigners made for a very interesting experience. Not to mention the maddening complexities and seemingly simplistic language that is tiếng Việt.
Anyway, on arrival I found I had to ditch my Boston way of living, that is to say pushy, impatient and blunt in favor of taking things slow, speaking with great subtlety and applying pressure in ways I had never considered. I got myself what locals call "a long-haired dictionary" (a girlfriend) and started taking lessons in Vietnamese. As I mentioned in this thread, at first I went to markets pretending I had a sore throat, pointing at things. I am Asian, so I could pass for a local, albeit a very tall, very muscular local, relative to the typical Viet guy of course. People also liked to comment on my teeth. Let's just say that dentistry is only now becoming very important. Who can blame them though, it's relatively expensive and until recently, could be quite painful.
Another weird thing was that people don't go to bars. Bars were introduced by foreigners, usually for foreign soldiers at various points in time and they have always been stocked with whores. Prostitution is pretty rampant there and locals tend to go to barbershops, massage parlors and karaoke places. Once I was taken out by a group of professionals who I was teaching, looked over and one of them was fingering one of the girls sent to keep us company. Ick. Anyway, this means that local people tend to think that most foreign guys, especially single ones are whoring all the time.
So, I definitely have a love/hate relationship with the country. I don't know if I could live there again, particularly since my last business venture failed through no fault of my own other, than partnering with an 82 year old friend who ended up dying and thus, so did the funding provided by grateful recipients of his compassion decades before. I will say that the experience of it all changed me and in many ways for the better. If I had no ambition, I would still be there, living in the same beautiful house overlooking the harbor that I'd never be able to afford living in, if it were located in the US. I often wonder if I've made a mistake trying to change my life for the better, but as they say, "no backsies."
I am often left wondering how I can use these experiences to leverage a better life for myself post-Vietnam. Vietnamese is a supremely useless language internationally, except for maybe speaking to Vietnamese people. I also wonder if my time there hasn't kind of killed my resume. I went when I was 22 and came back when I was 27. I just turned 28 and school seems like a dwindling option, but I really hope to get work in an international capacity so that's what I'm working toward now.
As I understand it, finding employment in the EU and getting a valid work permit can be tough for US citizens, but if you've got an in then it's relatively easy. If I could recommend one thing about living abroad, it's to have a plan. Get an idea of what you'd like to be able to do once you come out of the experience and allow for that plan to change. But, have a plan.