There may be good arguments for corporate tax cuts but Ryan's argument is not one of them.
The best way for the Federal government to create jobs is through policy decisions and subsequent investment. For example, if there were a national initiative to cut class sizes in public schools by 50%, that would create jobs now and the product of that initiative would create still more jobs in the future!!! If there was a national initiative to put six years of foreign language learning into every public grade school in the country, that would create jobs, etc. There are plenty of worthwhile jobs that can't be off shored, but vision is needed to recognize where they are, and policy decisions are needed for implementation.
Nothing of this sort can be accomplished now because these kinds of national initiatives require government action. The present administration views government as bad and so it has set out to dismantle government rather than make government more efficient and better. There are two very different philosophies at odds with each other and hence our current stalemate.