Ukrainian people insist on overthrow of the corrupt and criminal ukrainian government. The best way USA can help is putting pressure on ukrainian government, in partucular Viktor Yanukovych, the president, Mykola Azarov, the prime minister and members of party of regions which are contributing to Yanukovych's regime. Thw methods are:
Ban listed human beings from entering the USA and the EU
Freeze bank accounts associated with them and their oligarchs (Firtash, Kolomojskyj, Akhmetov and others)
Financially suport the riots on Ukrainian streets. (i.e. Supply the protesters with food, warm clothes)