A 20% tax on Facebook and Google isn't going to do anything. A 20% on Office 365 is meaningful but only until they find software alternatives from anywhere else in the globe.
As for the US, O365 will not be more expensive but the cost of producing O365 will be. It will be up to execs to determine if they want to pass the costs to the shrinking number of businesses or if they want to eat the cost of production at the expense of shareholders.
Either way, American society is going to eat the cost, either in loss of customers or in loss of 401k.