Every time the US government moves Bitcoin to Coinbase, the price of bitcoin in the market drops by 5% within 5 days of the move. And this has happened several times and the pattern is almost the same. However, it is their right to sell it because the US government is one of the 10 largest Bitcoin holders (and that too from confiscations).

uppss
Yeah, for sure that they have every right to sell specially Bitcoins that they have confiscated.
But I'm not sure if there is a pattern there, a lot of factors to look at when we see the price of Bitcoin going down, most likely, geo-political events and then the CPI every month could be just a few of them and it's not like US selling their Bitcoin.
In any case, it might be a good call to look at how much the US government had, as they are one of the countries that has a lot of Bitcoin in their disposal.