I think that there are several considerations at play here. First off, yes, in some ways it is an American thing, because reality is that walk-in potential converts to EO/EC OO/OC churches are vastly more common in the US or Canada than in the typical village church in the Old Country.
1. Inquirers to Orthodoxy or Catholicism (because one hears the same comments made by visitors to parishes of both Churches) who are coming from a Protestant background are, generally, used to the type of 'welcoming' to which someone referred above, as it's a hallmark of Protestant congregations. They may well perceive its absence as reflecting disinterest in them as potential converts.
2. Those who encounter the lack of this at a large Latin parish may well write it off to a depersonalized atmosphere resulting from a congregation numbering well into the hundreds. It's harder to do that in a typical EO or EC parish, with congregations numbered in multiples of ten.
3. 'coffee and' - by whatever name your parish terms it - is a relatively common phenomenon in our parishes and pretty reminiscent of the 'fellowshipping' that the inquirer knows from his or her Protestant background. In the Protestant world, that after worship fellowshiping is where the 'greeters' or the 'welcoming committee' takes up and follows through on those quick initial and hospitable moments that occurred on arrival. In our churches, too often, these are the times when our peoples break down to families or cliques (with sidelong looks over shoulders at the 'outsider' - or, as I've heard, in various languages, 'the Amerikan', or 'the Englisher'), effectively excluding anyone who isn't one of 'us'.
4. If the parish is one that includes a reference in its titling to an ethnicity - Russian, Ukrainian, Greek, etc - it's all the more likely that an approach by no one will reinforce the visitor's perception that - not being of that ethnicity - he or she is unwelcome.
5. It sure does nothing to disabuse that perception if the sole question directed at him or her is 'So, are you _______?" When one's answer of 'No', is met by a response of 'Oh, hmm, well have a nice day', it kind of cements the perception.
6. Finally, we are not used to - and really have no well-thought out plan on how to deal with - visitors, converts, inquirers. They are a relatively new phenomena to most of us. Historically, our Churches were, indeed, ethnic enclaves and those who came to us did so by marriage - with the occasional inquirer arriving at the priest's door. We did not, historically, reach out to convert - that was a Latin Catholic thing - not an Eastern or Oriental one - Catholic or Orthodox.
Now, in a world that is more aware of our existence, we need to get over wondering why people expect a different approach of us and do something about it if we are to grow and if we are to fulfill the commission to go forth and teach all nations. Fufilling that commandment involves more than missioning - or outreach. It also requires that we reach out with open arms to those who come to us, not merely those whom we approach.
We are naive if we believe that the Lord will not look askance at us if persons never had the benefit of learning about our faith because we didn't make them welcome among us.
Forget the red carpet, some warm words beyond 'hello' would suffice. "Nice to see you, is this your first visit to a ______ church?" - "Did you have any questions that I mught be able to answer? - etc.
PS it's also good if the interchange isn't conducted between the visitor and the parish eccentric - too often the case - or the person most likely to say 'oh, you're a ____, you know that you're doomed to hell, right?'