Very often it seems that transatlantic mail is weeks on end about arriving, either way. It is silly, when UPs can do it in one day.
Twenty years ago I wrote a letter to the Danish postmaster general. He agreed that transatlantic mail takes way too long, and said they are trying to work with the US postal service to improve it. Apparently it's a long project, or maybe they have only improved it with Denmark, not here in the UK. :-)