An employee who was acceptable to the company on X and unacceptable on X + 2 weeks is being asked to shoulder risks equivalent to that of an independent contractor or consultant. Many people enjoy shouldering the many risks associated with parachuting into foreign countries for two weeks to execute engagements with no guarantee that there will be work available on week three.

We are customarily compensated for shouldering these risks. It is one reason why consultants quote week rates like $10,000 as opposed to getting only $120k in yearly salary but very predictably actually getting that and its attendant benefits suite.

Half of the low-ball startup monthly salary offer plus no benefits plus no options doesn't even crater the approach to the bridge of the disruption this putative employee suffered to get him to the US.

While acknowledging that the US is largely an employment-at-will country and people can dissolve things for any reason or none at all at virtually any time, writing somebody a $4k check as sole payment for services rendered, after they've joined your company as an employee and been involuntarily terminated 2 weeks in, strikes me as deeply problematic.