Fashionista1
The Ukraine situation has been caused in part because there are still Russian speaking peoples who identify with being Russian and do not want to become Westernised or join Nato. From Russias view if all the bordering countries join Nato, then Russia could be seriously under threat and under the thumb to Europe. The Crimea, although annexed as part of Russia, is another potential threat to Russia's Black Sea Ports. It is not a simple solution and in my view nothing really to do with us. The US should be sorting this out.
There are enclaves of people all over the world who are living in countries that they are not entirely happy with. There's even Kaliningrad, which is a Russian enclave between Poland and Lithuania. Massing tanks on the border and rattling your sabre is not a valid way of protecting what they think their rights are - a natural extension of that would be for Russia to threaten Poland and Lithuania because their Russian compatriots are feeling a bit hemmed in.
Russia needs to stop thinking that everyone is out to get them and perhaps take on the concepts of democracy.
And as for leaving it to the US, nobody died and made them world police. Or is it just because Ukraine is a far away country of which we know nothing?