This may be a foolish question given my limited understanding of QM but here it is.
As I understand quantum entanglement basically means that two particles evolve as a single "unit", i.e., are described by a single wave function. Now, it seems to me that production of entangled pairs (or n-tuples?) of particles must be a common occurrence and assuming that these particles may then travel a long way away from each other, does this not mean that the whole universe must be a mess of entanglements, effectively breaking the principle of local action? I believe, I understand the reasons why information cannot propagate faster than light from one region of space to another in spite of entanglement but it still seems to me that a universe of "disentangled" particles would behave quite differently from the universe where many particles are entangled. Is there a flaw in this reasoning?