One major factor for the USAC enforcement of rule that International Cycling Union (UCI) licensed racers are barred from racing in other sanctioning bodies is well founded on insurance concerns. When a rider from the US races abroad on a UCI license issued by USAC they need to request permission from USAC (See USAC rulebook Appedix 3). What does that have to do with OBRA and ACA? Well, a lot. Allowing UCI riders to compete in OBRA and ACA events is undermining the insurance agreement USAC has with the UCI and transitively all other cycling governing bodies associated with the UCI. For example, when a US based rider decides to head on over to say, Spain, they show the permission to ride letter from USAC along with their UCI license to the fine folks at registration. Which is essentially saying, "Since the Spanish Federation is permitting this race, and the Spanish Federation is part of the UCI, I have insurance." Alternatively, if internationally licensed domestic riders were to continue racing in OBRA or ACA events, it is setting a precedent for riders from outside the US to race without insurance as they likely won't hold OBRA or ACA licenses and in this all undermines USAC's insurance agreement with the UCI.
An additional insurance concern comes from amateur riders, which is why USAC has some grounds on the basis of standardizing upgrades and categorization of riders across the country. By allowing category reciprocity from USAC to OBRA/ACA and vice versa, USAC is taking a big risk. This comes from how stringent USAC's upgrade process is, (or at least how stringent USAC believes the process is). That is to say USAC simply doesn't trust the upgrade process in OBRA or the ACA, and I think understandably so, as the process may be softer/weaker in OBRA or the ACA. Now, one could make the argument that this could be true for any local association (like NYSBRA, NEBRA, etc...) but at least local associations across the country are using the same rulebook and overseeing the process from top to bottom. And as far as USAC is concerned a category 2 road rider from OBRA or the ACA may actually be more like a USAC cat 3 and their lack of experience, pack riding skills and the like could present a great safety risk to other riders in a USAC Pro/1/2 field (such as a USACrits event), which is why we have categories in the first place. By removing category reciprocity USAC is making sure that they are covered for any event under a USAC permit.
One last note is on USAC's perceived lack of support for cyclocross because as USAC is prone to saying "cyclocross isn't an olympic sport," which it isn't (yet, hopefully). And while disappointing to many, it is a partially justified statement, this is due to the fact that USAC just like many other athletic governing bodies in the US is a subsidiary of the US Olympic Committee, which means two things. First, this sets the principal under which USAC operates, which is to win Olympic Medals. Second a good portion of the funding comes from the USOC, around $900,000 for fiscal years 2010, and 2009, making it the largest direct contributor outside membership fees, permitting, etc... for our governing body. Now, full disclosure, the second largest direct contributor is the USA Cycling Development Foundation, bringing in about $800,000 in 2010 and 2009. Now, as of July 13, 2011 delivering Olympic medals was removed from the official purpose and bylaws of USAC, but there is still a culture of olympic success in Colorado Springs, with the USAC and USOC offices being less than 7 miles apart.
In summary it's pretty easy to write off USAC cycling based on it's actions, but before getting out your pitchfork and regional flag declaring your independence from the tyrants in Colorado Springs, take a minute and think about why the governing body is making the changes you see.