Should America worry?
A Russian submarine has moored at Russia's base in Syria after a patrol mission while another one is getting ready to sail off after replenishing supplies — the rotation that underlines Moscow's growing military foothold in the Mediterranean Sea.
The naval base in Tartus is the only such facility Russia has outside the former Soviet Union. In 2017, Moscow struck a deal with Syrian President Bashar Assad to extend its lease on Tartus for 49 years. The agreement allows Russia to keep up to 11 warships there, including nuclear-powered ones.
I don't worry. A Russian flotilla based in the Mediterranean Sea will lead a short but exciting life during a war. Russia doesn't need a blue water fleet and trying to cling to one is foolish.
Personally I prefer to have Russian defense resources diverted away from the Baltic Sea area to a place where NATO and other allies unlikely to help in the Baltic Sea region (like Spain, Italy, Greece, Turkey (?), and to a lesser extent France) can destroy some of Russia's military power in the Mediterranean Sea.
Heck, Ukraine should probably consider Syria their first line of defense.
How much of Russia's Syria commitment has been done to justify the conquest of Crimea in the face of NATO opposition and economic punishment?