Proxy wars are nothing new. However, when you have the US empire providing intelligence, materials, money, as well as non-uniformed former(?) servicemen fighting and taking a part in an actual land invasion of Russia that is something entirely different.
When was the last time Russia and/or China sent Russian/Chinese mercenaries to fight or invade the continental US?
The Continental US is somewhat unique among large, powerful nations. Our geographic boundaries of the Pacific and Atlantic Oceans, The Gulf of Mexico to the South, one neighbor to the North, and one neighbor to the South makes us less vulnerable to invasions on our interior. I don't think other nations haven't thought about it, but our nation is too vast and varied to mount an effective invasion before we see it coming.
Red Dawn was pure fiction. We have too many eyes on our borders to not see a massive invasion force heading our way.
Can you point to any news sources that report a land
invasion by Ukraine into Russian territory? All i can find is a counter-offensive, meaning they are there to affect tactical and strategic goals, not to occupy it for good.
The only thing i can find is, after over 2 1/2 years of Russia invading Ukraine, Ukraine recently went on the offense and gained about 18 miles inside Russia.
In contrast, Russia controls about 20%-24% of Ukrainian territory with 3M-3.5M Ukrainians living under Russian occupation.