From Oslo to Doha, Riyadh to Moscow, governments that rode crude’s historic rise to unprecedented wealth are now being forced to start repatriating their rainy-day funds just to make ends meet. The halving of oil to less than $50 a barrel has the potential to alter one of the most powerful economic and political forces of the past half century: the rise of the petrostate. These countries led a surge in state investments in the U.S. and Europe that now totals about $7.3 trillion globally, according to the Sovereign Wealth Fund Institute. During the last boom, the oil countries flaunted their wealth abroad by buying stakes in iconic companies such as Barclays Plc as well as trophy assets including Manhattan hotels, European soccer clubs and London luxury homes, often in the face of opposition from the local public.