"How to make football popular in North America"
You must first grasp why it is so popular in the rest of the world. There are two reasons:
The first reason is simplicity... the lack of rules. When I was young we used a bottle cap as a "ball" and two trash cans as goalposts. We played on cement and didn't have gloves or special shoes. We didn't play with any rules like offside or a fixed amount of players on each team. But we grew up loving the game. Now I realise that in NA, every school/college has it's indoor gym and there are state/national champioships but in the rest of the world very few have that courtesy. In latin america, for instance, where soccer is king, kids grow up playing soccer in the dirt and there aren't any other alternatives. No baseball teams, no hockey teams, no basketball teams, no school tournaments, no state championships, just football with your friends. This brings me to my second reason: when you grow up playing and loving the game on football, you relate to other great players either of your national team or of the club you support. Now these ties to a team or individual players go much deeper than in NA. Soccer personalities become more important than political figures in less developed countries and kids dream of one day becoming great football players and playing in the CL final or the Mundial final. In NA one cannot relate the same way to football players because they are not of the same level an their european and latin counterparts.
Having said that I realise that american sports are more advanced than football and the matches are much more entertaining to watch. Teams in american leagues are much more balanced than in any other sports league in the world due to the implementaion of rules like the salary cup and the draft. I hate it when teams like R.Madrid go spending hundreds of millions each year to go buy the best players in the world. Moreover, all these sports are more offensive and faster paced than football and have frequent timeouts (which allows more commercials in between the action), so they are more suited for television.
Personally I am a HUGE fan on football, I would rather quit my job than miss one of my team's matches, but if I was born in the USA I wouldn't have any reason to watch football. I would watch NA sports who offer a greater spectacle. Not having a team to support or relate to wouldn't justify spending those boring 90mins 0-0 draws on your couch.
So in conclusion I thing that N.Americans cannot enjoy football like other countries because they have better alternatives and Europeans/S.Americans/Africans etc. love the sport because they are born into an environment where it is already popular and grow up playing and loving it...
Now would adding more rules help the sport in NA? I think it wouldn't. The main reason is that players would adapt to the new rules, making the USA/ Canadian national teams even weaker in international competitions (which would alienate even more possible fans of the sport). Furthermore, these rules would require dramatic changes in the football (as well as it's referees) causing it to be esencially a different sport. On the other hand FIFA and UEFA try to keep football as simple as possible (one example is not allowing camera assistance for the referees, instead just accepting the ref's error as "a part of the game"). They reaslise that in order to keep football as popular as it is worldwide you need to somehow relate to the kid that's playing barefoot in the dirt. Finally, I think that your rules would just lead to more hasty attacks and more posession turnovers which would in fact make things more difficult in offense. Especially the shot clock rule... you can't force an attack in football like you do in bascketball, you must first find an opening. Cutting down the time to 30min halfs would just be negated by the fact that you reduced the players in the field so they'll just do more running in less time (which i think is too low, every match would end 1-0 or 0-0). Not allowing passes to your GK would be an interesting change (even in the rest of the world) but I don't think would change much (once keepers were allowd to grab the ball with their hands after a teammates pass but they changed the rules so that they could make the sport more offensive so this is I think the only rule that could possibly me implemented).