Playing European TT in US ?

I have a Rega P3 turntable I bought while living in France. I have brought it home to the US and it is not playing right. I bought a 300 W converter to play it. At 33 rpms it plays too fast (about 43 rpms) and at 45, the belt shudders and it plays at about 20 rpms. Is there something I need to make this play ? something in addition to the converter ?

thanks in advance
A frequency converter as well as a voltage converter. Some power regenerators will change frequency. Europe is 50 hz, US is 60 hz. A new motor otherwise...
The pulley may be the problem. You may have a 50 cycle(Hz) pulley, and need a 60 cycle (Hz) pulley. If it has a synchronous motor, this different motor pulley would make a speed difference. Check into a 60 cycle motor pulley, if this is the case.
After looking at your table on the net, it appears it does have a synchronous motor. That means the AC power frequency (Hz) controls the speed. France has 50 cycles (Hz), the US has 60 cycles (Hz), so this would be the first thing (60 cycles or Hz pulley) I would check into.
I brought my Rega P3 (lovely TT) from EU to US and changed the motor (contact Rega and ask) - it's worthwhile and at least I got a more recent improved motor which enhanced the performance.