Immigrants from other countries embrace their heritage as if it's where they are from?
Are you sure that's what you meant to type? ...'cause if they're immigrants from other countries,
...
that is exactly where they're from! DAH!

For example i'm watching the Lesnar vs Cain pre fight stuff and all Cain talks about is being Mexican. Yet he's born in America. America gave him his opportunity and his life, not Mexico. I'm not saying he shouldn't be proud of his heritage because he should be, we all should be, but it seems a little disrespectful to the country you are from to do that.
That could simply be a backlash from living in a "mono"culture (for want of a better word)
...or in this case, more likely a publicity seeking schtick.
In Canada, I don't notice such profound examples. It could simply be because ours is a multicultural society where all cultures are valued & respected. Hence the compulsion for jingoism isn't as pronounced, ...or maybe there is just so much of it, ...I fail to see it all around me.
I have noticed these tendencies most often in those who feel their culture is undervalued or under threat.
Like marrying a girl and flirting with the cocktail waitress in front of her.
Now
THAT's tacky! Why do guys do that? As if you'd have any interest in them?

I also see this with Italian immigrants. Kids born here but tattooed up with Italian pride or the flag or some other sh*t.
I think when a people with a strong culture, a strong cultural identity, and a history full of great achievements with much to be proud of, find themselves in a new culture where their heritage is not given the respect they feel it's due... the jingoism is bound to come out in leaps and spades.
Unfortunately, this pride in heritage, can sometimes be misinterpreted as a slam on other cultures when it's not.
Also too, a culture and a country are two different things. You can love your country, but not it's culture.
By the same token, you can love your culture, but not your country, or what your country has become.
Don't take it personally.