I don't think that banning McDonalds plastic toys is going to save the planet
The big problems are in transport and electricity generation.
Look at electricity use in the production of say aluminium or glass, look at what is burnt by the shipping companies
I think your point is a good one - especially given the tax breaks on things like aircraft fuel but concentrating on little plastic figures misses the point.
I think the real answer to your question is that the man in the street is not likely to up sticks and move himself and jobs to a less responsible localtion as businesses are in this gloablised world.
Any government will therefore argue that controls have to be impose internationally so that one country doesn't try to sell out all the others .
This is why international agreements like Kyoto and Copenhagen are so important