I think that optimism is nice but ultimately unrealistic. We've seen several hundreds years so far of failure to achieve a revolution within the core, not a single one has succeeded. Not just the USA, all of them across Europe, Canada, Aus etc. This isn't caused by a lack of effort and it's not going to be resolved by simply trying all the same basic strategies (such as mass line) that have been tried.

I believe it is more realistic for communists to simply cripple the core in such a way that projects elsewhere in the world may flourish. Then the core can simply collapse as its power shrinks. It has demonstrated time and time again the ability to prevent the efforts of the left.

This is not a defeatist attitude, it is a "we should be focusing on a different strategy as the existing ones have proven uneffective" attitude.