So far I know gravity is relative to mass but what if Earth was shrunk into the size of USA shall we experience the same gravity and weight or more? If not how can Earth ever become a black hole? I have read that if Earth was compressed to the size of a 50 cent coin it would become a black hole that not even light can escape from it's gravity. It's confusing.
Gravity (force of) is proportional to each mass, true, but it is also inversely proportional to distance squared, distance from center to center of the objects.
So if you shrunk the earth down, to say, 1/4 its present diameter, then the distances are 1/4 what they were, so force of gravity is 16 (4 squared) times stronger.
Shrink it down to 1/1000 its present diameter, then the distances are 1/1000 what they were, so force of gravity is 1000000 times stronger.
you can see as size becomes smaller, force increases by a large factor.