Right now most support for Ukraine comes from European countries and not the US. The biggest single donor is the EU and its members donate even more individually. I can see Ukraine having a problem going offensive, but the support should be enough to not be overrun.

That is if Trump is elected, which is not a given. After all Biden has won an election against Trump before.

Even if Trump gets elected and Russia invades, the EU is far from being weak. The EU has more soldiers then Russia, with a bigger population, which are better equiped and a much bigger economy. Adding that to your enemies list is just dumb. Not that Russia is the brightest.