Joining NATO means there will be missile systems (etc) in Ukraine along Russia's border, ie a permanent hostile threat. Would you like those missile systems pointed at you 24 hours a day? Doesn't sound very friendly does it.
The US isn't NATO. If the US wants a war with Russia it can go it alone. Good luck with that!
Russia didn't have a problem with Ukraine until 2014 when a coup was organised by Western powers to overthrow president Yanukovych and his government and install a hostile regime in it's place. Remember Victoria Nuland being secretly recorded while discussing who would replace Yanukovych? Russia had to move quickly to protect the Russian speakers in Crimea, Donetsk and Luhansk who were being discriminated against. Russia also has a critical naval port at Sevastopol in Crimea.
This whole mess can be blamed on the US, UK and partners.
