That's what a PEO company can do for your business.
An HR department might be a nice idea to have in the office of today's "ideal" remote business world. What are you supposed to do if your company has less than 100 employees? If you're not an accountant or a lawyer — the chances are that even with all your experience and expertise on payroll and benefits, keeping track of US compliance (and other country-specific requirements) becomes too much work to handle yourself.