Politics have prompted at least seven companies – five of them American – to abandon projects, freeze activities or sell stakes worth billions of dollars in Libya, Algeria and Egypt in the past 18 months, according to a report at MSNMoney.

The politics of the Middle East and North Africa have made things more difficult for all companies but American companies are not tied to North Africa, said John Hamilton, North Africa analyst at Cross-border Information.

Two years of turmoil since the Arab Spring and some of the toughest terms in the business have led international oil companies to reassess their role in North Africa, with U.S. companies appearing to be among the keenest to leave, the report said.

Libya and Algeria are among Africa’s top four oil producers. Together with Egypt, they are major suppliers of gas to Europe and their budgets depend heavily on energy revenues.

But Libya has not turned into the bonanza some foreign oil firms had hoped for, while the cost-to-reward ratio of producing gas in Egypt and Algeria looks less appealing as new finds in more politically stable places like Tanzania offer alternatives, MSNMoney reports.

For some U.S. companies, the prospect of shedding non-core assets and cashing in on the shale gas boom at home seem increasingly attractive, analysts say.

Exxon said in September it was scaling back in Libya. Royal Dutch Shell abandoned two exploration blocks there last year. Both had made disappointing finds, the report said.

“That’s in contrast to companies to like Repsol, Eni, Total and even BP,” Hamilton said. “For them, these are large deposits on their doorstep so it makes more sense for them to stick it out.”

Labor strikes, militias and political activists have blocked several oil fields and ports since the end of July.

Marathon Oil said it would sell its stake in Waha Oil Co., a consortium with Libya’s National Oil Corp. and two other U.S. companies.

“Libya is an expensive place to do business,” said Beth Hepworth, co-director of Frontier Research and Advisory, which also publishes Libya Monitor. “To justify the tough terms, oil firms needed very good finds but even before the revolution, exploration results in general had not met expectations.

“Couple that with the deteriorating security environment after 2011 and the uncertainty over the political roadmap, and you get a toxic cocktail.”

In Algeria, a January attack on a gas plant in the Sahara desert triggered an exodus of expatriate workers and forced energy companies to ramp up security. But terms were already so tight that there was little appetite among international oil companies in the last licensing round, MSNMoney reports.

U.S. ConocoPhillips said in 2012 it would sell its Algerian unit to Indonesia’s Pertamina for $1.75 billion. Hess is selling one if its two Algerian oil stakes to Cepsa, which is already heavily involved there, and Britain’s BG Group also plans to leave.

In Egypt, two years of upheaval have hit government coffers, raising concerns that it cannot pay existing companies to produce its gas let alone entice investors to develop new finds. It plans to compensate the companies but that comes too late for some.

Apache Corp. said in August it had sold 33 percent of its Egyptian business to Sinopec for $3.1 billion following investor concerns over its exposure there. Apache has sold non-core assets globally to focus on U.S. onshore production.

For companies heavily invested in production, the decision to leave North Africa is not as easy as it was for Exxon or Shell, who were exploring. For many investors, particularly Europeans, it makes sense to stay on, the report said.

Statoil and BP did not abandon Algeria after the attack on their joint venture at In Amenas. Libya’s oil minister said this week that Eni, the top foreign oil company in Africa by volume, was committed to Libya and BP would soon resume its activity.

Germany’s Wintershall, involved in the Mabrouk joint venture, said leaving Libya, where it has been active since 1958, was not a topic of discussion.

“You are not in a position to say, ‘This isn’t fun anymore so we will leave,'” said a senior executive of a major energy company working in Egypt. “You have contracts, obligations, billions of dollars worth of investments. We don’t believe Egypt is going to go the Syria route.”