Let me tell you what i know:

There was the Mexican adventure. France gave money to Mexico (maybe not all of the promised money reached Mexico). Mexico was not able to pay it back and Napoleon occupied the country with French forces. He did not want to annect the country straight, therefore he made an Austrian nobleman Emperor: Maximilian. Well, the French troops were defeated by the Mexican people's army and Maximilian was killed.

I think he was very unlucky in internal policiy, too. As far as i have red (but this may only be history from a German view) he tried to provoke Prussia, because he thought he could easily defeat it and so solve the internal problems he had. He failed.