Not only geography but demography. Ukraine was part of the Soviet Union for something like 60 years, and for good or bad there are a lot of Russian nationals living there who have ties to Russia.
Most of the Ukraine was part of Russia when.Russia annexed Crimea in 1783 after an earlier war with Turkey... from 1783 until 1991 for a total of 208 years
By all means, let’s give Texas, Arizona, New Mexico and California back to Mexico.