I went to the 1998 WC in 98 as a kid (17) with my dad and his mate.
I went to the 2006 WC with my friends and to the 2008 EURO in Vienna with my work colleagues (company is owned by Austrians, still is).
I never experienced a tournament atmosphere outside of Europe, but in Europe, it's surreal.
All these fans, football culture, you feel safe and comfortable, etc. It was magic.
One of my friends is a guy who goes everywhere with the NT (or rather went, he's going much less often these days, has two kids)... But before that he went to S. Korea in 2002 and Brazil in 2014.
While it's exotic, he did say the overall atmosphere in Korea didn't match up, and that Brazil didn't really feel safe.