Why, according to Roosevelt, should
Americans care about what is going on in
Europe?

Because Europe parts of it, used to transport goods and resources to us Americans, without caring what is going in Europe, consequences and fears would rise. Back in WWII it was a huge deal, we only had heads up until Pearl Harbor broke down, later on WWII in Germany and Europe started.

president thomas jefferson commissioned the expedition shortly after the louisiana purchase in 1803 to explore and to map the newly acquired territory, to find a practical route across the western half of the continent, and to establish an american presence in this territory before britain and other european powers

bibliography and citations to credit the sources hope this you if not my deepest of apologize ^w^