The solution to enter any market in the USA is to buy an established business with several years in business.
The acquisition needs to be big enough in terms of income and employees.
When an established business is acquired, employees sent from abroad (expat) can obtain work visas legally.
Opening an office and hire (or send somebody from your country), can be very long.
Having a visa in the USA is essential before any office is opened.
https://www1.nyc.gov/site/internationalbusiness/how-to-open/open-an-office-in-nyc.page
Trying to sell in the US, with just a liaison and representative office, with a few newly hired employees (or expats) who must integrate in the ecosystem can be very long and costly.
Because of legal, social and economic aspects of the US, it is every inefficient to try to sell with just an representative and liaison office.