If you got lots of U.S visitors then I suggest you to use both adsense and chitka otherwise stick to adsense.
I applied for Chitika with my new website last night,but I was rejected after 8 hours,they said because my website is at begginning stage,they can't accept at the moment. It is no doubt that Google Adsense is the first choise for PPC ad platform,but as a webmaster I would like to see more good competitors of Adsense. You know Google's action they often ban account forever ,even if you don't do evil.So god bless there are 2-3 real competitor for Adsense.
Chitika is a close competitor to adsense. You can stay with Chitika as there's nothing to lose and I guess you'll have less fear of being banned without proper reason.