Well actually if you see the following teams :
Ratio of India : Pakistan (No indigenous players)
UAE - 50:50
Hong Kong - 40 :60
Oman : 15:85
Singapore : 70: 30
Canada : Mix of Ind, Pak, WI, Sri and few Canadians
US : Same as Canada, few US
Japan is the next nation on cards for non commonwealth spot, they have qualified for ICC U19 WC in January 2020. A mix of few Indians, Australians and around 10-15 native Japanese.
Also note there is a U19 Women's World Cup of 16 teams starting in 2021. Expect more of the Non commonwealth nations.China ,Indonesia(who have a women's cricket league from sub junior level, club cricket etc from this year) Brazil etc could qualify some day.