There's multiple levels of blame to be given. You can say China is responsible for 100% of all deaths, but you can also be critical of the US response and ask how many additional deaths were due to a botched Federal response and a patchwork state-by-state approach.

The fairest characterization would be to say both share some weight. We would expect China to have contained the outbreak to minimize the impact to itself and other nations, but we also expect the US to protect us from foreign viral/bacterial agents as a matter of national security.