The USART receive interrupt additionally requires the received data register to be read, before readying the interrupt for re-enabling from the return from ISR.
Try the following:
ISR(USART_RX_vect)
{
unsigned char c = UDR0; // clear the USART interrupt
// or UDRn, UDR0, UDR1, etc...
state_Led = !state_Led;
}