Apply for export in the US, get certificate for export, ship the aircraft to the EU, make an EASA compliant annual, register in any country. That is the easy theory. Reality can be quite bad. What year was the 172 built? The logs of a N-reg is most likely not sufficient to document airworthiness of the aircraft to EASA standards, so expect a significant 4-digit bill to straighten paperworks. Further on, if the avionics is not compliant to EASA standards, expect the next 5-digit bill to fit anything. It seldom makes economical sense to bring a C172 from the US into EASA space. So, it may indeed be wiser to sell in the US and buy a similar here.