I think calling it a "national issue" is a bit hyperbolic. As far as I can tell, it's had more legs here than anywhere else.
But, to your questions:
When did you start feeling strongly about women's sports? Why?
I don't I feel strongly about women's sports, nor do I think you need to. To me, this isn't sports issue, per se, it's a boarder philosophical exercise.
Did you think transgendered individuals didn't exist before?
I had a trans professor at UT, so yes, I was aware of the existence of trans people. But are you suggesting that trans women were participating in HS and College athletics before say 10 years ago?
How many people do you think this affects?
Define "affects"? There are about 8.5 milllion HS and collegiate athletes in the US. So, if roughly 3% of the population identifies as either trans or intersex, that's about 255k. But there seems to be less of an issue with female to male trans, so cut that in half and call it 125k. If you're talking about the "potential" of the US (not even gonna contemplate the world)... there are about 33 million biological males between the ages of 10 and 24, so that's just under a 1 million.
Do you think that sports bodies are incapable of developing rules to cover these very niche situations?
No. Lance Armstrong out front shoulda told you
Do you really think this is important enough that state and national legislation needs to be involved?
No, but that doesn't mean it shouldn't be addressed or discussed in public.
My solution is quite simple and certainly not new. Plato designed an entire republic on a similar concept.
Eliminate gender segregation in sport. Qualifications would be based on something akin to a SPARQ score.