Hmm. I don't know what to suggest as to who to read. The USA seems to have gone through a few different periods of alternating between aggressive expansionism and isolationism.

There was a great reluctance in the American public to enter either of the two World Wars, for example. The mood was isolationist. Woodrow Wilson eventually got the USA into WWI, assisted by angry public reaction to the sinking of the Lusitania by a German U-Boat. FDR eventually got the USA into WWII by I think quite deliberately provoking the Japanese into attacking the USA (by his trade restrictions on Japan). In either case a reluctant public had to be somehow maneuvered into supporting major foreign wars. Provocative incidents had to be either arranged....or waited for...as the case may be. (911 was another such provocative incident that had to be either arranged or waited for...not for me to say which, because I can't say I know for sure).

There were times when it was easier than that to get Americans to support a war. The Spanish-American War was a grand little adventure which had massive public support and was guaranteed not to fail. It resulted in America acquiring overseas naval bases in the Atlantic and Pacific...definitely a handy move for a nation bent on extending its imperial reach around the globe.

Another convenient little war on hapless Mexico secured the USA California and the Southwest, while Texas had already fallen into American hands after a brief period of independence.

The announcement of the Monroe Doctrine was indicative of a USA intent on dominating the entire western hemisphere (with the exception of Canada...at the time). It was announced as though it was being done as a favour for Latin Americans....an amusing notion!...it was really being done to establish the USA's sphere of influence in the world and to shut Europe out of that sphere.

So I'd say that the USA has swung back and forth between expansionist policy and isolationist policy during both the 19th and 20th centuries....but committed itself firmly to a "world" policy after 1945.

So, yes, the overall mood and psychology has changed dramatically since 1945. That's when the USA became the Superpower...and Britain had to face the end of its colonial dominance. By 1945 Brittania no longer ruled the waves...the USA did. The imperial crown had passed from London to Washington.

The Soviets attempted to dispute it, and their attempt failed after a horrendously expensive and risky 44 year campaign known as the Cold War.