The drone of US get shot down by Russian fighter.
Good teaching for US.
Really, How?
In fact, this may end up being worse for Russia in Ukraine. It has been reported that Russia plans to try and recover the drone. And while it is not likely that they'll recover enough to be of any use, let's consider the idea that they do.
Russia doesn't have the technological know-how to quickly reverse engineer it and put up their own version, so by the time they did, it would be obsolete compared to what the US would be then using.
Even then, the main reason the US has not provided Raptors( This type of drone) to Ukraine was to prevent the possible recovery of one by Russia. If they were to believe that Russia
had been able to recover enough to be of use to them, that would become moot. Raptors are capable of more than surveillance, and would be a game changer if provided to Ukraine, since as noted above, Russia would not have the time or ability to put up anything comparable to counter them.
As to the claim of Russia protecting itself from future invasion. Russia would not stand a chance in a conventional war against NATO. If you take the risk of a nuclear exchange out of the equation, NATO could easily invade Russia right now and Russia would not have a chance. Russia taking Ukraine wouldn't alter that one bit. (In fact, it makes things worse for Russia, as the material and personnel being wasted in this conflict weakens their overall military strength.)
NATO has no intentions to invade Russia, because:
1) It could turn into a nuclear exchange in which nobody wins.
2) They have no desire to saddle themselves with the eventual occupation stage that would follow an successful invasion.
Your arguments in support of Russia's invasion of Ukraine don't hold water.