a fresh astronomy enthusiast here. Recently I've been reading upon how immensely far other stars are from our solar system and how is it possible that we may be seeing stars that are already dead. My question is - if there is a star that is a millions of light years away from us and we are seeing it shine tonight, but in reality that star died long long time ago (perhaps also millions of years ago), is it possible that matter from that star somehow travelled through space to our solar system and at some point in history it collided with the Earth and now we're "made" of this star (made as in that star stuff is present here on Earth)? To me, I don't see reason why not, because even though matter cannot travel faster than light, my intuition tells me that the answer to my question is yes, it is possible that this could happen, (if only in theory) given enough distance. But maybe I'm not considering some important points which are obvious to more experienced folk.
Stars really are immensely far, however it's a common misconception that the stars that you can see are millions of light years away. Most of the visible stars are a few tens to a few hundreds of light years away.
However it is possible that there are stars that have exploded in a supernova: Eta Carinae looks to be approaching the end, and is 7500 light years away (so we see it as it was 7500 years ago). It's one of the most powerful stars in the milky way, but it is so distant that it looks like a faint star.
It is impossible for matter from an Eta Carinae supernova to reach the solar system before light from the supernova, because matter must be slower than light. No matter how far the star is, whether near or far, light beats matter in any race. In fact, Eta Carinae is too remote for any matter from its eventual supernova to ever reach the solar system.
The "starstuff" of which we are made was present in the molecular cloud that collapsed to form the solar system about 4.7 billion years ago, that molecular cloud was enriched with material from ancient stars that died during the 8 billion years that elapsed before the formation of the sun.
Earth has orbited the galaxy 16 or more times since the planet formed. Given that even stars in a single open cluster usually have somewhat different velocities relative to galactic center, it's highly doubtful that we can see stars made from the exact same starting material as earth. As for the supernova that delivered the compression wave to our stellar nursery, it's likely too dim by now to be seen for more a few dozen parsecs, and might be located nearly anywhere.