You'd use one of any of the following expressions: 'it's in vogue' or 'it's fashionable' or 'it's the in thing' or 'the latest thing is...'
eg: In Italy the latest thing is to eat sushi
In Italy it's in vogue to eat sushi
In Italy it's the in thing to eat sushi at the moment
Sushi is the in thing in Italy at the moment
Sushi is all the rage in Italy at the moment
So what's the latest Big Thing in Italy? Oh, I heard that it's eating sushi...
People are going crazy for sushi in Italy at the moment