Russian broke the Budapest Memorandum
which was signed by Russia, UK, and USA
therefore, the United Kingdom and the United States must comply with their obligations as long, as Russia does not return territory under the control of Ukraine
The world is always on power games, It's just about who wins.
The modern borders changed rapidly in the 20th century. Many new countries formed while some old countries lost their existence.
Historically and Demographically Crimea is Russia and it is better with Russia than Ukraine.