I wouldn't say it's impossible to get a work visa - I've gotten TN1's before, and am currently on a L1-A with a few months left before my Green Card is finished. I received my L1-A 2 years ago when I was 22, now at the age of 24 it took roughly 8 months to get my Green Card under the EB1 classification.
Yes - this is where having a partner in the US is really helpful. My partner was able to setup our holding company, and I was able to work for it for a year and then go for my L1. We are then able to start smaller organizations in which VC's can own their percentage, and rest being owned by our holding company allowing for things to still be legal for my current Visa situation.
It's a little bit more complicated to setup, but well worth it and allows you to qualify for a Green Card much faster than the traditional avenues. I'm not sure YC/PG's standpoint on adding this layer of complexity to the incorporation procedure they undergo with YC Funded Startups, but I'm sure that if the team and idea is good enough they'd work with you on this.
