Another difference is that American crafty houses are roasting lighter than in Italy. For whatever reason, Americans are following a different craft and not optimizing their espresso recipes nearly as well as the Italians and not using the same goals and procedures as they do.
And frankly I'm convinced some of the roasters simply don't know what they're doing. They've been told that roasting light is good, and they don't realize that light roasting with espresso brewing is risky. Especially with bean types that are known to be acidic.
Another note, isn't the ratio for espresso in the States different than in Italy. When I was a barista in Chicago we did 1:2 coffee to water. I thought I heard that in Italy 1:3 or 1:4 was more popular. I may be wrong
Not sure about the authority of this page:
> Most of these Italian blends (Illy is the exception) clearly make effective and imaginative use of coffees of the robusta species
http://www.coffeereview.com/italy-seen-from-america-nine-gen...
http://www.lavazza.co.uk/uk/at-home/blends/caffe-espresso.ht...
(Lavazza has a number of other "100% arabica", including Qualità Oro that is more or less the golden standard - pun intended).
http://www.segafredo.it/it/a-casa/caffe/moka/emozioni-100-ar...
Illy we already said.
I personally don't wander beyond these three vendors (Segafredo is from my hometown, Lavazza is the most ubiquitous, Illy is the mainstream high-quality choice), but there are likely more. To be fair, there are also a lot of Robusta mixes as you go down, but the "100% arabica" brands is firmly at the high end.
I also grew up with italian espresso and I always wondered why all these crafty, specialist roasters (all over the world) can't do a drinkable espresso and always end up with undrinkable acid in a cup.
A lot of italian espresso blends are a mix Arrabica/Robusta. Robusta beans create the sought-after strong/bitterish italien espresso flavor and probably also reduce/mask/balance the acidity.
Robusta beans according to the crafty roasters are low quality garbage, and they only care about arrabica beans. Clever marketing by the arrabica industry? Robusta beans have a bad reputation because they are majorly used by cheap coffee brands - but not all robusta beans are the same either.
So because third wave/hipster coffee shops only do arrabica, but italian style espresso needs a blend. That's why we can't have a good things.
I simply order espresso machiato when i want an espresso, the bit of milk foam reduces acidity to an acceptable level.
There is a longer article somewhere on nytimes about this topic. can't find it anymore.