Unless you happen to have an air con system (rare but they do exist) that works on European power you have to find a way to supply US style power to the system.
EU power is different in two ways. The voltage is 240V instead of 125V and the frequency is 50 Hz instead of 60 Hz.
Some of the ways to get US power.
1. Diesel generator
. If you are already in Europe
might be hard to find a US style 125V, 60 Hz generator
2. Power converter. You can buy a big box that will input EU AC power and convert both the voltage and the frequency to US standards.
. This works like a generator in that it makes the US style AC power but from your existing battery
system instead of from a diesel motor
. But downside is it draws a LOT of power from your batteries so you will have to have a very, very large battery charging
system to keep the inverter