Welcome, Todd!
There's a bit of a discussion on dist advance
in this thread that sort of talks about the same thing.
Not only is the total advance between the Euro and US dists different but so are the curves. Off the top of my head, for example, the Marelli S 103 B, as fitted to early US Spica cars, provides only like 7 degrees primary advance at 1400-1700rpm while the Bosch 044 Euro version gives almost double the primary advance of the Marelli at a lower 1200-1500rpm (or something like that). I'll draw up and post a graph later tonight when I can see what the specs actually are.
What model Alfa are we talking about?