American policy is concerned with retaining the single world power status gained with the demise of the Soviet Union. To that end, Russia must be contained. The American aim is to push the NATO sphere of influence right up to Russia's borders (remember Georgia).

The EU doesn't have a foreign policy. When it comes down to it, EU member states are American vassals and the EU as an institution reflects that. EU enlargement is a tool for US policy (further supported by neoliberals who want the EU watered down to a big free-trade area with no political or institutional capacity).

The US-NATO thrust doesn't worry about busting countries up. The EU is supposed to be the helping hand for those countries. But the EU has long since discarded any ideals in that respect. So helping Ukraine will be the EU's responsibility, but nothing at the appropriate scale will happen.

Russia's concerns do have their merits, but Russia has been keeping Ukraine in a state of corrupt dependence for decades. The notion that there is any real help there for Ukrainians is illusory.