The risks to health faced by Americans long ago are different from those we face today. Some of the things that once killed many people (like poor sanitation) now kill many fewer. On the other hand, we now face new risks (like death from auto accidents) that didn’t exist a century ago.
The chart below from the WHO’s Global Health Risks illustrates this point. Traditionally (many decades ago), major risks included under nutrition and unsanitary water. Over time, as standards of living increased, these kinds of risks diminished.
But, others took their place and now include health risks from tobacco, lack of physical activity, and automobiles, among others. However, not all risks affect all people. A lot depends on where you live, your income, education, and other factors.
Likewise, the risks faced by people in developing countries are not the same ones present in developed ones. The chart below, from the same WHO report shows deaths attributed to 19 risk factors by income level of country.
Relative to higher income countries, low income countries have more deaths from underweight children, unsafe water, and unsafe sex, for example. But higher income countries have more deaths attributed to high blood pressure, tobacco use, and physical inactivity, compared to low income countries
The bottom line is that it is not possible to quantify how much various factors affect health once and for all. It depends on context and can change even within a society over time