You'll see this amore in parts of town where an ethnicity forms a majority or close to it compared to where people are a small minority in San Diego. I don't know about other places a whole lot. There is a Mexican flag painted car at a taco shop I go to sometimes though. At least here in southern Cali people aren't super big about their specific European heritage in my experience even the people whose families immigrated here more recently though the more recently immigrated families tend to be Jewish from the former Eastern Bloc and many left because of antisemitism and so it's pretty understandable that they wouldn't have as much Russian or Ukraian or Moldavan etc pride at this point.

So I live in a suburb that is probably 85% white and then mostly the rest Asian with a few people of other backgrounds living here as well and of the people that live on my little street of 11 houses we have 8 White families, a Japanese family, a half Chinese half White family and a family that has a 1/2 Japanese, 1/2 Jewish mom(no idea her specific Jewish ancestry like Ashkenazi, Sephardic etc and she's also half Japanese so that makes it harder to tell I think she's European Jewish though) and a Christian European dad. I don't think I ever discussed the ethnic heritage of any of my White neighbors with them and I've lived here for decades. And to answer the question further I've also never seen any flag but an American one so I couldn't tell you the ethnic heritage of any of my non Asian neighbors. Other factors that sort of play into not seeing a lot of flags is a lot of White Americans whose families have been in the country for a long time won't actually know their specific ethnic background and can really only guess by their last name and virtually no Black Americans who are descendants of American Freedmen know their specific African heritage either so you will almost never see them fly the flag of a specific African country either.