1.sustained R&D of engiens needs supports of billions-dollar infrastructures such as tunnel systems,testing-beds and labs...
only those countries with huge economy and revenues can afford those expensive infrastructures,such as USA,former Soviet Union, CHina today and Japan.
In fact, even anyone of Germany ,UK and France can not afford such expensive infructures,so they set up EU and unite to develope aircraft industry.
2. only huge demestic demand can assure the order and repay of huge investment on a new aircraft project.
now, only those huge counties ,such as USA, CHina ,Russia , India and EU(if united) have such huge demand of aircrafts.
the domestic demand of UK, Germany ,Fance and Japan is quite limited,so it is uneconomic for them to develop 5G bird.
Instead, USA ,CHina ,RUssia and India has huge demand for 5G bird, so they develope it..