China's territorial expansion in the South Pacific and support of anti-American political parties in e.g. Cuba and Venezuela is certainly enough to warrant Stephen Colbert's suggested title "frenemy", not to mention their continued international temper tantrums over the status of Taiwan.

It should be noted that the US put an end to colonial expeditions in China with the Open Door Policy in 1899. The "Century of Humiliation" article enumerates complaints about the colonial expeditions but does not mention any US actions or the ODP, the latter, I assume, being considered not humiliating. It's hard for me to imagine why the US should be lumped in with Britain/France/Russia/Japan in the period before 1949. After that we were at Cold War, of course.