whats the best usa prepaid sim for eu
 

and why.....

I'm not aware of any US prepaid SIM that works in the EU. T-Mobile certainly doesn't. AT&T doesn't even roam in Canada.

I don't know of any US prepaid SIMs that work outside N. America. One decent solution would be Celtrek. It's an Israeli SIM coupled to a US phone number.

i thought that prepaid AT&T s working in abroad

It doesn't work in Canada. I think it does work in Mexico, but that's the only place it roams.

Get a T-Mobile SIM and a UMA phone (I have the Samsung T409) and use it over Wi-Fi in Europe. Advantage: You can use it, at normal US rates. Disdvantages: It's a fiddly technology that sometimes doesn't work perfectly (but most of the time it's just fine), and you have to be near a reliable hotspot to use it.

Is there a phone for T-Mobile that supports both UMA and T-Mobile's new 3G network at 1700 MHz?