The question of federal tax on the individual/corporation depends entirely whether you are "engaged in a trade or business in the United States". It's one thing the CFAs get wrong so often when advising non-resident aliens.
If a 1-member US LLC belonging completely to a non-resident/non-citizen hires a US person (from the IRS standpoint) to be the managing manager for the sole purpose of opening an account for the company in a US bank, and that person does not get any salary from the LLC, does this make the company ETBUS?