This is the result of false propaganda spewed by US-corporate-mainstream media about Russian actions and intentions in Crimea and Ukraine.
The Pew/USA Today poll conducted over the weekend found 53% of the 1,501 Americans surveyed were in favor of stepping up economic and diplomatic sanctions on Moscow for its March annexation of Ukraine's Crimean peninsula and reported instigation of the separatist actions roiling eastern Ukraine.
"... reported instigation of the separatist actions roiling eastern Ukraine." The only thing reported was false propaganda. A few US officials claim they think Russia is instigating Russians in Ukraine to be pro-Russia versus pro-EU and NATO. The people are ethnic Russians who know what's gone on in Kiev. They know that the US spent billions setting up the conditions for the violent overthrow of the democratically elected leader of Ukraine, for whom they mostly voted.
Most Americans are fed state propaganda through mainstream media. They don't read or watch world news from any other perspective. They only hear one story that is hammered into them and brainwashes them.