Yes they were
No they weren't
Technically yes. All of Europe was involved, and I mean all of Europe, and there were two smaller theaters in India and the Caribbean. There was some fighting in northern Africa as well.
there were theaters in India the Caribbean and if you count the war of 1812 north america and it was all over Europe.
I can see why people say they were, but compare them to the actual World Wars, not nearly so many nations participated.
The wars was fought by European countries, regardless of where the battles took place the only countries involved were european