Earning the CFA charter would be helpful if the position you are applying for requires the candidate to be a CFA charterholder. In order to provide sponsorships to foreigners, companies have to prove that they are unable to find a US resident/citizen with the required qualifications. Having the CFA charter as a requirement would decrease the pool of US qualified candidates, hence, increase your chances.
However, if the position does not require the candidate to be a CFA charterholder, then it isn’t much valuable in terms of helping you get a work visa in the US.