Yes, you can compress any object small enough and you end up with a black hole. And yes as far as anything else in the solar system is concerned, if the earth

Yes, you can compress any object small enough and you end up with a black hole. And yes as far as anything else in the solar system is concerned, if the earth was compressed into a blackhole no orbits would change. Well relativistic effects mean there's no stable orbits below 2 radii (maybe it's 1.5), so various sats would get sucked in. However just because that's true, doesn't imply the earth is a blackhole, just that the orbits in the solar system wouldn't change. Similarly if the sun collapsed into a blackhole the earth's orbit wouldn't change, but it would get much colder.