The revolts of 1830 and 1848 were based solely in France. Spain was never involved in these revolts, so this is true.
After the collapse it become a "democratic" nation so US saw it as less of a enemy. Also, it become a lot weaker so it wasn't as big of a rival or threat to the USA. Allowing it to trade and work together on major projects.
Tariffs on imports
The 1920s presidents began a system of tariffs on imported good to encourage spending on American goods only. However, with no trade, European countries were unable to make money.
Tariffs are taxes on imported goods. This is a common economic policy of conservatives.
