Second what benignuman said. I would add to other things:
First, Rav Broyde even identifies three acharonim who say that haircovering is optional.
Second, in much of the world including the US, trousers have been women’s garments as long as they have been men’s garments, and indeed they are the standard modest wear for women in most of the Muslim world; this is not a recent phenomenon. In the California State Railroad Museum there is a photograph from a century ago of female railroad workers; every single one is wearing either trousers or overalls. For a long time women had to wear trousers designed for men, but Levis introduced their first jeans designed specifically for women, the 701, in 1934. The target market according to the company was women who worked on ranches and farms, but they quickly caught on in a much larger market and were actually featured in a *Vogue* article in 1935 as casual wear for women!