Over the years I have visited France, Belgium and Italy whilst wearing traditional tartan kilts as well as contemporary Utilikilts, and I have never yet been barred from Churches, Cathedrals or any other buildings. One consideration could be that I am not really a T-shirt type and so would have been wearing Polo or conventional leisure shirts in subdued colours, and would have been wearing kilt hose with shoes - not boots!

I have visited Spain and The Balearics many times but, alas, that was before the days of my full-time kilt wearing, and so I was not kilted whilst there.

Show reasonable and considerate respect for the country you are visiting, and its peoples, and you should survive unscathed!