Silly conspiracy theories the last few pages of this thread.
1) The idea that the Russians would "strategically" pull a highly competitive skater just to avoid potentially losing to Alysa Liu is ridiculous. I think they have more confidence than that in Sinytsina, especially since Liu's skating has its own shortcomings. It's usually not Russian nature to back away from a fight.
2) The idea that the Americans would deny Sinytsina a visa for a junior ladies skating competition is similarly ridiculous. As said above by someone, that US officialdom would even care about figure skating teenagers is beyond belief. US officialdom doesn't even care much about sports and medals.
3) Please stop saying Sinytsina was denied entry to the USA. SHE WAS NOT DENIED "ENTRY". What she was denied was EXIT from Russia due to her documents not being acceptable to either Russian Exit Immigration or the airline taking her. Somebody on the Russian end at the airport looked at her visa and/or other documents and saw a potential problem that might mean her denial into the USA if she reached there. Airlines get fined large amounts (like $10,000 USD) if they board someone ineligible for entry to the destination country, so all over the world, documents are scrutinized carefully before allowing someone to board, especially if en route to a country known to be finicky about visas like the USA. (Russia is also finicky about granting visas and entry to foreigners, so don't play the victim there.)
We don't know the exact problem. I doubt if the US Embassy issued her a visa that was timed to spontaneously combust as she reached the airport. It's possible her visa was not a multiple entry. It's possible that it was, but expired prior to travel or was due to expire during the competition. Or it was a new visa that somehow didn't match (name or other info) her ticket or supplemental non-visa documents. Stupid mistakes due to inattention happen all over the world to all nationalities, every day. Ultimately, the traveler (or her adult proxies) are 100% responsible for double- and triple-checking that all documents for travel including transits and destinations, are acceptable. Sorry, but the goof up for this almost certainly lies on the Russian end of things.