It was the United States which pioneered the idea of the modern mail system
The UK had a general post office that deliverd to individuals over 100 years before the USA was founded. The US postal system is based on the UK one that delivered their mail before the US’s founding. Why on earth would you think the US pioneered it?
My opinion is that the probability of life developing on another planet, advancing to interstellar travel, and being physically close enough to us to visit us during the last few million years is so implausibly tiny that anyone seriously asking about their relations with human beings can be safely dismissed as a complete rube.