The USA has a long (perhaps entire) history of putting itself first:

It also has a history of putting dictators in power. And, it has a history of abandoning support when it suits them.

Why would it be any different now?

It wouldn't. I don't think that the world should "rely" on the US at all.

I don't think is anti-war though. I think he recognises how valuable war is, but also that it loses some value if US has to directly get involved. WW2 was them selling to both sides as well, until Pearl Harbour.