Being the world reserve currency soaks up dollars, which dents the inflationary effect of deficit spending and Fed expansions.
Bush started the stripmining of that privilege, Obama is worse by 10x.
A currency can be the world’s reserve currency while not being the currency in which oil is priced. The biggest example of this is sterling before World War 2. The dollar has always been the world’s oil pricing currency, even when it was not the reserve currency.