Why is China not an ally to the US other than the fact that it is a growing economy may be too big for US? What happens if US does not want to contain China any more? Are there fundamental issues which will put China and US as enemies?

China is communist and systemically atheist. That's basically it. Americans have always (or at least always since WW2) viewed communism as an existential evil and themselves as chosen by God to eradicate it from the world by any means necessary.