Except that the US isn't composed of 327 million 39 year olds, it's composed of a fairly even mix of people of various ages. If you multiply the case fatality rates from your link [1] by the population in each age bracket [2], you come up with a projected CFR of about 1.8% in the US, assuming that a similar fraction of people in each age range are infected.

       Age  | US Pop |  CFR  | Est Deaths if
            |        |       | 100% infected
    --------+--------+-------+--------------
     0 -  9 | 40.01M |  0.0% | 0.00M
    10 - 19 | 41.97M |  0.2% | 0.08M
    20 - 29 | 45.43M |  0.2% | 0.09M
    30 - 39 | 43.63M |  0.2% | 0.09M
    40 - 49 | 40.46M |  0.4% | 0.16M
    50 - 59 | 42.83M |  1.3% | 0.56M
    60 - 69 | 37.41M |  3.6% | 1.35M
    70 - 79 | 22.66M |  8.0% | 1.81M
    80+     | 12.68M | 14.8% | 1.88M
    --------+--------+-------+--------------
      Total |327.08M |  1.8% | 6.02M

1.4% is believable with those numbers. 0.06% is not plausible at all in the context of those numbers.

[1] https://ourworldindata.org/coronavirus [2] https://www.statista.com/statistics/241488/population-of-the...

It is impossible to calculate this from just the medians. John Ioannidis estimates a range of 0.025% to 0.625% by comparing the age distributions. However, there is so little data that any small systematic error could completely invalidate this.