Language, unified market, cost of making calls or sending sms, payment networks.
I'm sure there are scammers targetting Europe, but the US is a better market, because you get more people with one language, voice calls and sms are nearly free, and the dominant payment networks have a global footprint.
For Europe, you need a different language per country (more or less), calling cellphones and sending sms can be expensive (depends on the country), and victims may have country specific payment networks that may be hard to integrate from outside the area (lots of direct bank payments, which isn't easy to integrate with).
I'm sure there are scammers targetting Europe, but the US is a better market, because you get more people with one language, voice calls and sms are nearly free, and the dominant payment networks have a global footprint.
For Europe, you need a different language per country (more or less), calling cellphones and sending sms can be expensive (depends on the country), and victims may have country specific payment networks that may be hard to integrate from outside the area (lots of direct bank payments, which isn't easy to integrate with).