You need to be careful on how you define R&D. Pure R&D, the kind of culture that spawned say UNIX, Oak (Java) or Plan 9 etc is on the decline as in recent years the bean counters tend to look at pure R&D as a waste of money as there is no medium term return on investment. Look at the decline of IBM Research in the US as an example. Google and in some cases Microsoft are exceptions to this.

However the US tax code allows companies to write off new development of new systems as a tax break, so you typically would be doing this kind of R&D at a startup until the system moves into production and is then accounted for differently for tax purposes.

So US companies invest load of cash in R&D, just not the traditional kind of Pure R&D.