I'm pretty sure we'd see his/putins troops movement if expansion were the true motive.
Wonder how fast the US would occupy Mexico if China started building bases and hosting rockets pointed at us.
Discussion
Narcos: Mexico on Netflix dramatizes the point quite effectively that ever since WW2, the war on drugs has provided a cover story that allows the US (via the state dept and CIA) to weaponize the cartels and the DHS (Mexican DEA) to keep the Russian Empire out of our hemisphere. In other words, Mexico is already under pseudo-occupation.