Looking at this, singles between 18 and 44, there's just a massive amount of men compared to women: http://jonathansoma.com/singles/#1/6/2/0
For people between 18 and 44, the number of men very closely matches the number of women. So, ignoring polyamory, the the proportion of singles across America must be very gender-equal. Since that shows that the proportion of singles in cities in male-skewed, the proportion of singles elsewhere must be female-skewed.
You can have the same number of men and women and the older women have a hard time finding a man and the young men have a hard time finding a woman.
It makes sense if you think about older men and younger women being able to easily match up and older women and younger men not being able to find anyone.
I'd guess also more men than women migrate to the US for work.
Men used to die in large number from war and work, not so anymore.
So here we are.
The ratio of men to women in the US is almost exactly 50/50 (with a slight bias to women!) In fact, that ratio has gone down in favor of women over the years[0], which invalidates your last point. And unless you live in a select few states[1] this holds true.
Instead of there being a secret gender imbalance cover up, it seems much more likely to me that cities with large tech industries (like NYC) are just swimming with sausage.
[0]https://www.census.gov/prod/2001pubs/c2kbr01-9.pdf
[1]https://www.statista.com/statistics/301946/us-population-mal...