One of the things that most irks me, as an expat, is when someone claims that an entire country full of people are rude or lacking in manners. I guarantee you that if you go to live for even a short period of time in another country, you will notice general cultural behaviors that are different from your own culture; some will seem odd, and others will seem rude. I can also guarantee you that for every odd cultural mannerism you notice, the natives around you will notice at least one or two about you. With the right attitude, these cultural differences can add to the adventure that is having foreign friends and traveling and living abroad. I suspect that no matter how long you live in a foreign country, some of your native upbringing will still make you seem strange to other people long after you've learned all the local slang and lost any accent. One problem that seems common among Americans living in Spain, for instance, is saying "gracias" way too often. The Spanish actually get annoyed by this. Shopkeepers often seem confused when I involuntarily thank them after a transaction.
When you visit other cultures, the people will, by definition of being from a different culture, seem rude to you, and you will seem rude to them.
Lest you think I'm implying that Americans are much more polite than Spaniards, let's look at another set of customs: the dinner party.
When you are a guest in someone's home in Spain, there is an unspoken rule that you shouldn't ask for anything to eat or drink, and that rule is remedied by the expectation that the host will offer you things to eat and drink. Americans have this same system to some extent, but where Spain and the US diverge is at the dinner table.
In the US, when a host lays out a bunch of food on the table at a dinner party, the guests more or less understand that it's all for them and they can ask each other or the host to pass the potatoes if they want more. In Spain…not so much. A Spanish guest will tend to eat only what he is expressly offered to take. As a result, proper hosting etiquette is to constantly suggest that people with empty plates take more food. Sometimes it's even considered polite for a guest to decline food that he really wants to give other guests, or the host, the option to take it. Since both parties understand this, a polite host will continue to persist even after the guest has declined.
Personally, this drives me mad. I really can't stand customs where no doesn't mean no. I prefer to tell the truth and not have to repeat myself. But, I have to remind myself that I am in a different culture where my host is only being polite. It takes effort. And I'm not the only one. My wife had the opposite problem of waiting for food to be offered to her in the States, and sometimes walking away from the table hungry and annoyed at how rude Americans can be. Now that she and I fully comprehend the cultural difference, we know not to get annoyed, or, if we do, that no one is to blame but ourselves.
When you visit other cultures, the people will, by definition of being from a different culture, seem rude to you, and you will seem rude to them. If you can't bend your mind around to the opinion that experiencing and learning about these differences is the very thing that makes traveling and living abroad so much fun, then you should go back to your hometown where everyone behaves just like you.
This ad for HSBC got a lot of airtime back when I was living in England. It illustrates my point perfectly and humorously.