I absolutely think we are a melting pot. A pot of people from all over the world live together pretty much in harmony. When America was first being created we were a unique country open to people from around the world with freedom of religion and no royalty controlling us. That was the ideal we set anyway, of course there were some big hiccups.
People tend to couple up with people who have similar cultural values, and not surprisingly people from the same national background tend to be culturally similar. Usually, we see immigrant groups become Americanized by the third generation. Once they are culturally “American” it is more likely they will marry other “Americans.”
Personally, I see mixed cultural marriage all the time. I am white, Eastern European Jeiwhs American (2nd generation on one side and 3rd on the other) and my husband immigrated here and he is Mexican (his grandparents from Israel, France, and Spain). My neighbors at one house I lived at, the wife was Dominican and the husband Italian. Both of them came here around age 20. My sister dated a German guy for a while, she also lived with a man from the Philipines for a few years, my Mexican BIL is married to a man from Scotland. My neighbor is Lebonese-American and her boyfriend is black, although very light skinned, he might be biracial, not sure. Not that it matters. Another neighbor who moved away a few months ago, she was white and her husband black. I know many many people who are American and one parent is Italian and the other Irish. I think they have the Catholicism in common, and they settled in some of the same parts of the country. I dated guy in high school who was Ecuadorian-American. Many of his relatives married “Americans.” He married a Mexican girl his first marriage and a Greek girl his second marriage. My cousin lived with a Puerto Rican woman for many years. She actually had been married to a white Jewish American before the relationship with my cousin. She converted to Judiasm and raised her daughter Jewish even after they were divorced. My zumba instructor is Filipino and her husband is American. Pretty much I have the United Nations around me, and that includes intermarriages.
Pretty much everyone I mentioned about is an American citizen, but I used America to mean white European American when referring to “mixed” relationships.
Ugh, no one beat me up that something might sound racist, it’s almost. Possible to be PC when discussing this without having to write out really really long explanations for each person. I think what I wrote is easily understood who I am talking about. Hopefully.
Some groups feel it is important to preserve their ethnicity and they encourage their children to marry in the same nationality, or religion, or whatever. It’s tough to do for many generations though.