When an autistic American teenager falls in love with an Italian girl, he must overcome his difficulties with social interaction to win her.

I think of Rosie for this story.

Could be they are brought together for work / situation but must overcome awkwardness so she can see him as interest potential.

Not sure if you watch the Good Doctor, but the main character who's autistic finally wins over a non-autistic colleague who can see his goodness and is comfortable with directness and mannerisms but it takes time and his constant desire to improve himself.

So definitely good groundwork for a story - maybe just create the details of the situation - someone autistic already implies awkward so probably don't need to add that but raise specific struggle with this particular person and why her....

How realistic is the premise?

Isn't one of the defining characteristics of autism? an inability to relate to others, to even establish emotional bonds with anyone, certainly strangers (which the Italian girl would be).? Isn't it more realistic for her to get interested in him first?? So that her task/goal is to get him to come out of his shell and emotionally bond with her?

Just staying.

Agree. These thoughts should add up and clarify if this is a romance where the two spend significant time together or if he loves her from afar and it's more about him building up the courage or trying to get her attention.

Clarify the setting. If it's in Italy, better to say so. Though if it is, what's the purpose of an additional conflict? Seems a language and/or cultural barrier would distract the main struggle. Regardless of where, describe the girl in a more meaningful way.