Some countries (e.g. Russia) develop fighter aircraft (e.g. Sukhoi) with 2 engines.
Is it for maneuverability, or is it because they can't build an engine that would meet the power requirement?
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Taking the Sukhoi Su-35 for example, it has two engines, each capable of producing 86.3 kN of dry thrust, combined they produce 172.6 kN. With afterburner they produce 284 kN (142 kN each).
The jet engine on the American F-22 produces 156 kN with afterburner, close to the 142 kN of the Su-35.
Soviet Union / Russia made the Kuznetsov NK-32 military jet engine, capable of 137 kN (dry) and 245 kN (wet).
So, the ability or technology to make a powerful jet engine is not the reason. It's just powerful engines are much bigger.
The main reasons for selecting a twin engine design are:
As pilots, we very often go right for the aerodynamic reasons, but one glaring reason has been omitted from the discussion - price. Governments have to choose between having a smaller number of more expensive, likely more capable, aircraft and having a larger number of smaller, lighter, less expensive aircraft. This applies not only to initial cost, but also to ongoing maintenance, parts and fuel cost to operate the aircraft. The F-16 is a great example of an economically efficient aircraft that can be operated by nations on a budget due to its small size, single engine and availability of parts versus an engineering marvel like the F-22 which is no longer in production due in no small part to the difficulty of obtaining parts, a better explanation of which follows here: https://www.defenceaviation.com/2016/05/why-did-the-united-states-stop-f-22-production-could-lockheed-martin-restart-the-production-line.html
Also, along economic lines, a quick visual price comparison is found here: https://www.popularmechanics.com/military/weapons/news/a25678/the-cost-of-new-fighters-keeps-going-up-up-up/
Price issues aside, from a pilot's perspective I don't think there is a pilot alive who would not want a second engine for many reasons, but we aren't the ones buying the jets.