“if communism is so great why did it fail everywhere”

It hasn’t, there are still successful socialist projects in the world. When you bring that up, they switch to discrediting those; you simply point out that Cuba has a higher literacy rate, life expectancy rate and lower child mortality rate than the United States despite their poverty, to which you can point to the fact they’ve been under relentless sanction and embargo…making their achievements in spite of American action.

“Communist were just authoritarian”

*"But the anti-authoritarians demand that the political state be abolished at one stroke, even before the social conditions that gave birth to it have been destroyed. They demand that the first act of the social revolution shall be the abolition of authority.

Have these gentlemen ever seen a revolution? A revolution is certainly the most authoritarian thing there is; it is the act whereby one part of the population imposes its will upon the other part by means of rifles, bayonets and cannon — authoritarian means, if such there be at all; and if the victorious party does not want to have fought in vain, it must maintain this rule by means of the terror which its arms inspire in the reactionists(reactionaries). Would the Paris Commune have lasted a single day if it had not made use of this authority of the armed people against the bourgeois? Should we not, on the contrary, reproach it for not having used it freely enough?"* ~ On Authority

“China is just as bad as the US”

China has a higher life expectancy, higher literacy rate, higher home-ownership rate, higher protein consumed per capita and generally better social services when you compare the average of the U.S (including the deep south). The great transportation in this nation and infrastructure is an outlier where wealth is concentrated while productive forces build it for all.

Hope these help, comrade!