I really recommend that you read my article about Donald Trump first.
After that, you should carefully consider if this matters to the US voters.
My point being, it is better to have a united and a US friendly Europe, than a Europe split by nationalism and Putinism in some parts. Also, if the European countries would feel that the US was either isolationistic or somewhat negative towards the European Union countries, then some might turn towards Russia and break with the Union.
How would that affect US business opportunities with the worlds largest economy? And how about access to the Eurasian continent?
Just saying that a democracy is never better than 50.1% of the people showing up on voting day.
Just as a reminder, watch this trailer from the movie Idiocracy.