According to Google, the average English Premier League player has a salary of about 4.1 million pounds, or roughly $5,500,000. The average Women's Super League (women's equivalent of the EPL) makes about 47,000 pounds, or $62,900.
When we're talking about building US national teams from the best American (or mostly American) men and women players out there, it seems logical to me that aside from appealing to their sense of patriotism, we'd pay them according to the market rates. It seems logical to me that if you are asking a guy making $5.5m as a soccer player to risk an injury during the summer playing for the USMT, you might have to pay him more than you would pay a woman player who is taking the same risk with her $63,000 per year job.