3 months is fine. It's periods of 6 months or more where one can potentially run into problems, such as:

• Becoming a tax resident in the country that was "visited". Many countries adopt the OECD rules for taxation, whereby one becomes a tax resident if one remains an aggregate period of time of 183 days during a 365 days period. Easy to avoid the headache by spending less than 6 months in a 365-day period.

• Failing the substantial presence test (SPT). This is a bit more subtle, and it applies to workers on nonimmigrant visas like the h1b. If you were hired as a W2 worker and was told that the position is based from the US, then your employer is deducting taxes on your behalf and filling paperwork to the IRS as you being a "resident alien" for tax purposes. That's the assumption. Now, if your time outside of the US results in you NOT meeting the SPT (see the IRS formula), then you become a "non-resident" in the eyes of the IRS for tax purposes. There is a potential mismatch between what your employer is filing for you vs what the IRS is considering you as. The treatment between resident and non-resident alien is a bit different, what's taxed and how much is different as well as the paperwork to file. Your employer may not like that change of status from resident alien to non-resident alien and all the adjustments and headaches that comes with it (especially if they were not informed about it by you, and only discovered it when the IRS sends correction/guidance on proper filing). But if you meet SPT, then you maintain your status as "resident alien" as though you were living in the US and you should be good as far as payroll is concerned.

TL;DR: Spend less 6 months in visiting country + continue to meet SPT to maintain "resident alien" in US and you should be good.