He said the arrival of large firms like MTV Viacom, which recently bought Channel 5 for £450 million, and the sale of scores of independent production companies was a threat to the system that made them successful in the first place.
One such firm, All3Media, which makes shows including Skins and Midsomer Murders recently accepted a £550m offer from US firm Liberty Global which owns Virgin Media and US entertainment group Discovery.
Giving the keynote James MacTaggart Memorial Lecture at the Edinburgh International Television Festival, he said the UK's free-to-air channels had become "the must-have accessories, the tiny dogs of 2014, amongst US media companies".
Mr Abraham said: "I believe that it's the brilliance of how we, in this country, have balanced public and private risk taking that has set free the creativity and talent that the Americans are so keen to invest in."
Using the example of the 1990 BBC drama House Of Cards which was recently re-made to huge critical and commercial acclaim by streaming service Netflix, he said: "Would Netflix, for example, have bought a show about a murderous politician who broke the 'fourth wall' of drama if the BBC hadn't taken that risky decision, decades before?"
He went on to say: "My second point is that this system now risks becoming a victim of its own success.
"While UK production is an undoubted commercial success story, I wonder if it will continue to be a creative one.
"Scale demands an increased focus on cost-cutting and margins."