If congress overrides the copyright of the network you can indeed get a Tulsa station outside of its DMA. This is the same as if you lived in a white area in a DMA and the satellite provider provided you with a New York station even though you lived in OK. In fact the way the distants law is written the provider can pick any affiliate and provide their signal to any white area without that stations consent, or the consent of the network.
The key here is that the local station does not sign an agreement, its signal is picked up and retransmitted without its consent. It does not have any say so in the retransmission. Congress has in its power to say that any person in OK can get any network signal. The stations are using the public airwaves and any copyrights they have are granted by congress and can be taken away at the whim of congress. The only way for a station to prevent congress from doing it is to stop transmitting on the public airwaves... Or of course lobby congress to get the law changed to its favor (which the NAB has been very successful at).
As noted by ThomasRZ and Greg, your argument fails for several reasons - ownership of copyright material by the Network being the primary issue.
And I see you have taken the NAB line hook, line and sinker, which, as noted from the affiliate agreements, its the network that do not want public choice - although now with retransmission fees coming into play, virtually all stations would fall into protecting their DMA.
And until a year or so ago, the networks had dropped out of the NAB for about 10 years as they felt the NAB had a different agenda than they did - so this was not a NAB issue.
So once again, the NAB myth continues to permeate with no facts in reality.
Also also noted, you can put on secondary signals legally - although the network programming must be pre-empted - just as ESPN blacks out sports.
This is done in markets such as diverse as Palm Springs (which has Palm Springs and Los Angeles) to Salina Kansas (which has Topeka and Wichita) available on cable.
There is nothing stopping a station anywhere from signing a retransmission agreement with any MSO in the Country - however, they can only do it for programming they have legal rights to - and in most cases that is little more than their local news.
And, with retransmission fees, most stations would love to be on more systems - you just won't get network programming (and in many cases some syndicated programming) from them.