Recalling that at the time Panama was ruled by military strongman Manuel Noriega. The US role in his having power, and in removing him can be discussed further in another post. No one misses him.
I just looked up the numbers. Panama has a rate of 17.2 murders per 100K population. That's 5.5 * the US rate (although might be comparable to some inner cities), a bit higher than Nicaragua, much lower than Guatemala, El Salvador and Honduras. It is comparable to the rate, 17.0/100K, of Guyana, which the U.S. has never intervened in.
In GDP/capita, Panama is a little behind Chile, and ahead of Mexico, Venezuela, Nicaragua and several other nations.
In Economic Freedom Panama is ranked near France, Thailand and Trinidad and Tobago. Economic Freedom includes being able to open a business and not get hassled by corrupt government, and is correlated with improvements in quality of life.
Quoting the Readers Digest, "It pays to increase your word power." That would be vis-à-vis.
-- A fuller look at the Monroe doctrine would recognize that it was declared to stop European colonization and intervention in the Americas. The British sometimes helped. Most famously, the US helped the Mexican government of Juarez to resist and expel the French. The more recent past is complicated...