It’s always been a push-pull situation with immigration. The successful immigrant ancestor is part of the national mythology, families pass down the stories of arrival (hence, I know why the Irish in my family came here six generations ago), and the contributions of various cultures have contributed greatly to our society. On the other hand - there’s a part of human nature that is suspicious of those who are different. New immigrants often do not know our subtle social customs and can offend us without intending to. There is friction between the customs of different cultures that range from Dueling Food Odors to problems such involving practices accepted elsewhere that are illegal here. On the whole, though, immigrants have an easier time gaining social acceptance here than many other places. Some immigrants, in fact, do extremely well: Ahhhh-nold, Henry Kissinger, Bob Hope just to name some well known ones, but the rags-to-riches story does happen, people arriving with nothing and retiring millionaires. Doesn’t happen to everyone, but the possibility is truly there. It’s also there for people born here into dire poverty - where you are born and who you parents are does not limit a person here the way it does other places.
In a country like Japan, you have to be born in Japan and to Japanese parents to be a true citizen. Contrast that with the United States - anyone can become a citizen here. And not only can you arrive here and become a citizen, but we don’t require that you give up all your heritage and childhood customs, either. Families pass down food, traditions, and other aspects of ancestral culture for generations here and it’s seen as perfectly acceptable. Indeed, there’s a certain pride many of us have in being “mutts” and having a heritage comprised of more than one culture.
Nonetheless, it can be quite frustrating to deal with a new arrival who doesn’t speak a language you do, and may not know certain customs. And, if you’re unemployed you might, indeed, feel resentment if a new arrival has a job and you don’t. You might resent your nieghbor for being employed when you’re not. And, since immigrants can rise rather rapidly in wealth, power, and influence they can, indeed, challenge an old and established order.
Correction: you have a right to opportunity, you do NOT have a “right” to success. As it says in the Declaration of Independence, all men are created equal - they don’t necessarially end that way. You have a right to life, to liberty, and to the pursuit of happiness - it’s up to you to catch that elusive little butterfly.
Although our system is not perfect, we do try to maintain a situation where folks really do have that opportunity.
I honestly don’t know if we’re more generous or not.
In some ways, we may appear to be, but it may be more a matter of capability. We do enjoy considerable wealth, so we are more able to donate money and goods to someone else in need. We have some impressive technology - and we like to show off our accomplishments a bit and if we can also do a little good so much the better. And many of our citizens were either born abroad or still have ties to family and another nation, and so have an interest in those places that might lead them to contribute.
Maybe that’s part of it, too - although abroad there might be a stereotype of Americans as big, blond-haired blue-eyed people were not - there isn’t just one American face. Since anyone of any nationality can come here and become a full citizen - and it seems at least a few from every country have done so - we are less likely to see someone from halfway around the world as somehow inherently alien and forever foreign. Certainly there are people here who came from a different continent than my ancestors, but they’ve been here longer than my family has been . My family was “alien” much more recently than theirs. Wherever I go in the world everyone I meet might one day be a fellow citizen of my country. There are many citizens I see and work with every day who look different than me, speak with heavy accents, and yet they are still part of my country. So, someone looking different and sounding different may not make them as alien to our society as might be true elsewhere. If you’re less likely to help folks that look “alien” and “other”, the flip side is that the less strange and foreign they seem the more likely you are to help them.
But don’t forget that Americans genuinely do want to be liked by others. Maybe it’s our relatively informal society. Maybe it’s our tolerance of folks being different from us. Maybe we do it just to annoy others. As ruthless as we can be at times, we have this strange compulsion to help even our enemies. After the civil war, the North didn’t imprison the rebels, they sent them home. In WWII we bombed the crap out of Germany, then helped rebuild it. We also bombed the crap out of Japan, helped them rebuild, and provided medical care to the survivors, including flying many of them to the US for reconstructive surgery. When Chernobyl happened, we had US doctors lining up to go over to the USSR to help out any way they could even though our respective countries were still very much adversaries. Yes, at least in some ways, we are generous.