BSN as mandatory for entry into the profession and or holding a RN has been going on for over 40 years and it hasn't taken yet, and is never likely to any time soon. What has mainly happened is diploma schools
have pretty much died out, and Associate programs have beefed themselves up to provide the sort of nurses hospitals want.
IIRC, according to the lastest figures, over 50% of new graduates of United States nursing programs
last year came from two and three year programs, a number that has remained quite stable over the years, though perhaps down from say the 1980's and before when a higher percentage of RNs would have come from diploma or associate programs.
Quite honestly, and not trying to put down any particular group and or school, in order for there to be a mandatory BSN, the United States would need to educate more students coming out of high schools able to handle four year college/university course work, in particular when it comes to nursing, math and science. This so far has eluded the US educational system. When you consider it takes the average four year college student five or more years to graduate (leaving aside financial and personal matters), not everyone wishing to become a nurse has that kind of time.
Hospitals are still the largest employers of nurses in the United States, thus have great power in terms of dictating what sort of nurse comes out of nursing programs. If they all wanted a BSN nurse, schools would have no other choice than to comply because students wouldn't bother with a program where they could not find work after graduation.