A couple of things here. First, it's not uncommon for those of us in the states to wait well over a year (or two) to receive replies from celebs living in the states. Second, almost all the people you mentioned (I'm not sure about Holland or Cumberbatch, who are both British) are well known NOT to sign through the mail. This is not meant to sound mean, but barring some sort of miracle, you'll never receive replies from Leonardo DiCaprio or Tom Cruise.

Hi!
I've sent to Leo DiCaprio and Tom Cruise letters from Hungary on July the 28th, and I still haven't got them back.
Plus I've sent to Jimmy Fallon, Cumberbatch, Nolan, Zimmer and Tom Holland letters to on November the 18th, no feedback.
So the questions are: Does it take a lot more time to get back a letter if it was sent from Europe?
Usually how many days it takes to get back autograph from this type of celebrities (very famous, doesn't have much time)?