Of course, the only way governments worldwide will be able to control 51% of Bitcoin's hashrate is if they unanimously agree on using Bitcoin is a "One World Currency". This may all sound crazy, but we cannot ignore it from happening in the future.
They can if Chinese government, example takes over all the hashrate from miners in China. I don't think it will happen. They can not do such thing in dark ways and don't let the world know about that. They will slap on their faces by doing this.
However I don't feel surprise if governments in nations that are sanctioned like Iran, North Korea have run Bitcoin mining farms. They have nuclear power and the Internet. What they need is ASICs and here they go with Bitcoin mining.
What you ask is not impossible but I don't think it will happen in near future. Moreover, if it happens, we might see reaction from the community. Governments are always behind the community with creative idea.