It's a bit more complicated if you actually work for a US company, as I do in their UK branch, as there are substantially more laws that US companies have to comply with on behalf of their foreign-based employees such as the US's Foreign Corrupt Practices Act.
My company's travel department advises against travel to countries that are on the US's sanctions list if I still want to be sure of getting into the US on the Visa Waiver Program [sic] as a US company foreign employee. Cuba is softening as far as the US is concerned (unless the Republicans get in next time who have stated they will go back to the way it was) so I may get the chance to go there at some point.
If you don't work for a US company this doesn't affect you.
http://www.usatoday.com/story/news/politics/2015/11/30/us-tightens-visa-waiver-program-response-paris-terror-attacks/76564038/