Bitcoin is known as to be the biggest cryptocurrency. in some countries it can be used to purchase goods and services and some see cryptocurrency as a threat.
if Bitcoin comes to be number one currency in the world today, can it be hijack by the government?
Technically governments cannot do anything about bitcoins as long as INTERNET stays decentralized. But, governments may impose all kind of regulations on all types of crypto related entities. But, when people get into P2P level of transactions alone then government restrictions will become void. So, there are less possibilities for governments to hijack bitcoins in any means.
They could probably intervene with the ISP and tell them to block any bitcoin websites but honestly most of governments aren't that competent and usually it's also hit and miss since it could create another problem in the future as well and when it comes to P2P as you mentioned just try to look at torrent out there, despite all the effort being spent to keep people from torrenting illegal file they still can't do anything, the only thing they can do is just to find one by one who's accessing what and bitcoin p2p gonna be a lot more complicated than torrent.
They just not gonna able to contain crypto and block it because it's basically out of their abilites.