Bitcoin is the largest supercomputer in the world, with over 1ZH/s. I doubt that even a well funded collective of governments could attack it at such a scale. One of the advantages of ASIC mining is how efficient it is compared to FPGA, GPU and CPU mining, which makes attacks much more expensive. I heard they're going after DOGE next. It's Scrypt algo like Litecoin, but with more hashrate.