Either way I'd expect fewer americans still work at large businesses than at small and mid-sized businesses combined.
And "small businesses" with fewer than 500 employees represent 99.7% of all businesses and yet they represent less than half the total workforce.
Also, it's not because a company is small that the owners are small time business people. The owners might be independently wealthy.
Being an entrepreneur means getting things done with what you have. You don't need to be wealth and instantly go from 0 to 1000 employees. Most people start with modest means and build up from there.
So not only do most Americans do work for multinational companies (53%) but on top of that, 80,5% of the ones working in SMEs are themselves the owners and don't have any employees to speak of.
Which leaves a whopping 19.5% of American SMEs which actually employ workers.
So you're dead wrong.
cf: https://www.sba.gov/sites/default/files/advocacy/2018-Small-...