I’m just some dumb ol’ American dipshit, but I’ve thought the same for a couple years, now. Most DNA calculators give my family members who’ve tested some Balkan or South Euro along with our East Euro, so who knows if they were Croats that came to the Czech Republic centuries ago. I’ve traced all his familial lines back to Bohemia as far back as the late 1700s, but according to this wikipedia article, a bunch of Croats fled to the Czech lands in the 1500s.
His paternal haplogroup is R-U152, which is traced back to Northern Italy, I believe. Not that that means much of anything.
As for his cap, unless he picked it up on a visit to the motherland in his youth, I think it was acquired in the USA.
A couple other pictures of the old guy: