Are you planning to put 24/7 news on your main channel, or an HD-2 sub-channel?
We had an AM in the Salt lake market running BBC for a while, but it became a "gap-filler" for an FM, then was purchased by the Catholic Church. It did fairly well when they had BBC World Service, but I don't know if the BBC can service a commercial station.
You might want to look at some other outlets, like Deutsche-Welle (DW) radio from Germany, or Radio Netherlands English service, and maybe mix it with hourly news of American interest. Another possibility would be World Radio Network (WRN), which carries a selection of International Broadcasters news and features programming.
But, even with these kinds of first-rate international broadcasters, you'll likely need to grab something fully American each hour. But, you'd be surprised how much American news they do carry...especially on the political and economic front.