Enemies of the United States could benefit with any cutting of the Pentagon’s budget. It could also benefit if the budget is not altered. Enemies can make good use out of any action or non-action taken by the Pentagon or any other government establishment. Benefit is what you make of it. Enemies want to claim to be as much in the advantage as possible, either way.
I do not believe the United States' enemies benefit from cutting the Pentagon's budget. The government wastes billions of dollars each year and realistically these programs could run for much less if something was done to stop the over spending. Waste is cut when budgets get slashed, it doesn't give more opportunities to our enemies.
The DOD's defense budget is, shall we say enormous doesn't' capture the magnitude of the thing. The enemies of the United States will still be outmatched and outspent and outclassed should they want to engage the United States. No country has ever funded their defense to such an insane degree.
No, I believe that even with a slashed budget, the United States will always be the most powerful nation in the world. Take for instance the fact that our military budget encompasses the next ten or so nations. That's quite the might. It would not matter if we cut even a lot from the Pentagon's budget. Our enemies would still be afraid.