No, USPS doesn't collect import duties on toys for personal use. If you imported an entire alibaba shipment, then yes, as it would be a commercial transaction.
An individual personally? Buying ponies off the Internet? Yeah, the US is lucky (and a bit spoiled!) like that... pony collecting is a LOT cheaper for you all! Imagine if every time you ordered something online, there was 5-10% more tax thrown on it...