Part of being a parent apart from keeping your kids save is exposing them to things that are outside the ordinary yet beneficial.
Every time you learn from a new experience there is some period of discomfort as you pass from what you have known into what you now know.
Part of the reason clowns are feared is because, well one reason is that they are simply painted hyper insensitive idiots trying to get by in the world but more importantly that vague fear that comes from a natural distrust of the unusual.
But without it growth is impossible.
Europe is old and it's social norms go back a long way. American culture simply lacks this.
To go about your day and be confronted by some creative celebration that isn't sponsored loudly or isn't advertising is a declaration on a deep level to parents and kids and everybody that our individual imaginations are gifts in their own right. That wonder often follows moments of disquiet and that our world can be generous.