The incredible amount of carry on bags/hand luggage in the US is indeed the problem. Many European airlines enforce draconian regulations about what can be brought aboard the plane. They then call for all rows to board at once, which seems disorderly but works pretty well when many passengers have absolutely nothing to stow in the overhead bins. Not that I advocate harsher rules about carryons in the US, but if the rules in place were enforced it might help matters.