Yes, this can be a pain. There are some contracting companies that handle this for you, but that can involve hiring people in other countries as contractors, not employees, having an extra intermediary that handles their payroll and whose incentives in terms of quality service may not align with yours, etc, etc. Plus of course regulations about how long you can have people contracting for you before you have to hire hem as employees and whatnot.

Also, it's not just tax implications. There's also complexity about time off (vacation and leave regulations differ a lot across the globe), conditions under which people can or cannot be fired (or hired), differences in terms of non-salary benefits that must be provided, etc.

A simple example of the hiring/firing thing: under French law, if someone is on maternity leave you can't fire them. You also can't hire someone on an indefinite-term basis to do their job while they are on leave. Hiring someone for the specific term of the leave seems to be OK. See https://www.globalworkplaceinsider.com/2017/05/do-employees-... toward the end, though the whole article is a great illustration of some of the differences in this area between French and US law.

And then there are the fun parts about general regulatory compliance. As a simple example I've run into, the US _requires_ you to collect and report data about the race of your employees (see EEO-1), while the EU _forbids_ collecting this data to start with, last I checked. So you have to have distinct processes for employees in different jurisdictions, your HR database needs to handle these differences in rules, etc.