It might not be trust or customer service... it might be that americans have rights afforded to them via credit card laws. You can initiate a chargeback against the vendor and get your money back.
And for fraud... in the US you can lose max $50 to a credit card fraud incident ($500 if you are really negligent) by law.
So I think americans enjoy protections not available in other parts of the world.
I actually think this makes good sense. It eliminates the need for people "to take things into their own hands", or be overly cautious, so spending is increased.
I think it was matt ridley's book the rational optimist (?) that said that trust correlates with trade.