It's really not that - people have a fundamental desire to take action to mitigate tail risk even when that action poses more actual risk. You have to look at risk-reward tradeoff across the population. Treating the entire population for a disease very few of them have will almost certainly yield more (and potentially more harmful) realized side-effects than the actual primary effects being caused by the disease itself. Especially when patients aren't seeking treatment, so are most likely asymptomatic.
Ditto testing low-risk populations for all sorts of conditions they mostly don't have. Even a test that is 99% accurate in a high-incidence population is going to be utterly ineffective when applied to the general population. Bayes theorem tells us this. The side effects up to and including death of investigating or treating these false positives adds up to a real net-negative situation.
If it was even an eency weency bit better to treat in the US I would say they would overwhelmingly do so because they'd be sued into the ground otherwise.
tl;dr: especially when it comes to treatments, action is not always better than inaction. Generally, the US medical system tends towards action.