115V to 230V converter
It is in principle possible to run a 240V load off a 120V supply using a transformer.

However you must understand that transformers can trade off voltage for current but they can't magic power out of thin air. The feed supplying the transformer must cover both the power requirements of the load and the losses in the transformer. Power is proportional to voltage times current (if the power factor was 1 it would be equal to voltage times current).

In other words if a transformer is converting 120V to 240V then the input current will be more than double the output current.

The problem you will run into is if an air conditioner designed for the US market requires 240V then it probablly requires more power than can be supplied by a normal domestic socket. 


  I am looking at this unit  https://www.amazon.com/Frigidaire-FFRH2522R2-Window-Mounted-Room-Conditioner/dp/B00VV2JORQ/ref=sr_1_10?s=home-garden&amp;ie=UTF8&amp;qid=1525402023&amp;sr=1-10&amp;keywords=16000+btu
   https://www.frigidaire.com/Owner-Center/Product-Support--Manuals/?productCode=FFRH2522R2


https://www.frigidaire.com/Owner-Center/Product-Support--Manuals/?productCode=FFRH2522R2 claims that unit takes 11.3 amps, double that and add some overhead for the transformer and you would be looking at around 25 amps from your 120V supply. Regular domestic sockets in the USA are rated at at best 20A and more commonly 15A. Furthremore those are only intermittant ratings.

Sorry but you either need to find a smaller AC unit that will run off a normal doestic socket or you need to get an electrian in.